Hi all, sorry for my long period of absence.
In that time I've been experimenting with using a gunner for LD (yes, a pure gunner), and I did come to a few interesting conclusions, which I'll put down here.
Anyone is welcome to add to the guide some of their interesting (and potent) LD strategies, or to correct me if I'm horribly mistaken.

The Lockdown Gunner Guide
Generally, I've noticed that few actually resort to guns in LD (at least, T2 LD), and even fewer play gunners with extreme potency.
These days, while the priority for quite a few of us may just be killing off the opposite team and capturing as many points along the way, do remember that Lockdown is a team game - and with sufficient teamwork, a good gunner can make all the difference in a single team (I kid you not).

Cons of a Gunner
1. You have very bad damage.
---------------------------------------------------------------------------------------------------
More often than not (particularly in the lower tiers) gunners are not respected on the team because their damage output is mediocre - good gunners can clock in about 2k on average in a T2 match.
That being said, though, just like bombers, low damage doesn't necessarily mean they are useless. I'll get to this point later.
---------------------------------------------------------------------------------------------------
2. Gunners are priority targets for the enemy team.
---------------------------------------------------------------------------------------------------
You WILL draw a lot of attention to yourself should you use a gun - same applies for bombs.
Once you are out of the way, the battle becomes a lot smoother for the enemy - so be cautious when playing, and try not to be overly aggressive.
---------------------------------------------------------------------------------------------------
3. No teamwork = useless gunner
---------------------------------------------------------------------------------------------------
Probably the most fatal flaw of all, if your team isn't willing to work with the gunner, or if you find yourself alone a little too often, you won't make a significant difference to the match no matter how good your gunning skills are.
---------------------------------------------------------------------------------------------------

Pros of a Gunner
1. You can hit things that are normally out of others' reach, or considered too dangerous.
---------------------------------------------------------------------------------------------------
When you have 2 or more Guardians camping on a point, the last thing you'd want to do is to whip out your sword and charge in blindly. This is where the Gunner comes in handy - whip out a gun to disperse them with ease. If you're fast enough, you can even wipe both of them out before their shields have time to recharge.
---------------------------------------------------------------------------------------------------
2. Good gunners become extremely intimidating in-game.
---------------------------------------------------------------------------------------------------
Just like a Bomber, a viable Gunner can easily disperse crowds, effectively area cancelling all the entrances to a capture point.
And I think all of us would know better than to charge through a wall of bullets - with a gun, you can force Guardians to keep their shields up, prevent recons from sneaking around you, and even keep poised Strikers at bay.
---------------------------------------------------------------------------------------------------
3. Gunners are extremely versatile.
---------------------------------------------------------------------------------------------------
With the right combination of guns, your gunner can effectively switch roles to become a disabler (that is, dishing out debuffs to players), an area canceller or even a DPS (this is mainly in T3, though).
---------------------------------------------------------------------------------------------------

Basic Rules for a Gunner

1. Teamwork. Always stick with your team.
---------------------------------------------------------------------------------------------------
As a good gunner, your main focus in-game should be the whereabouts and strategies of your team.
Remember that a gunner mainly serves to complement the team - and done right, you can make your team far more effective in pushing for points.
---------------------------------------------------------------------------------------------------
2. Always keep moving.
---------------------------------------------------------------------------------------------------
Sounds a little daft, but trust me, the last thing you want to do as a gunner is to keep still for long periods of time.
That being said, if you're using a gun that forces you to stay still to fire, you're probably better off with something else.
---------------------------------------------------------------------------------------------------
3. Always shield cancel.
---------------------------------------------------------------------------------------------------
I always notice that mediocre gunners almost never shield cancel when gunning.
Reloading presents a window of opportunity for an enemy to attack - so if possible eliminate any of these windows.
---------------------------------------------------------------------------------------------------
4. Play smart, not aggressive.
---------------------------------------------------------------------------------------------------
I stress this again: as a gunner, your main priority is not damage. Going aggressive with a weapon that deals significantly less damage than swords is probably a very, very bad idea that gets you killed most of the time.
---------------------------------------------------------------------------------------------------

The Gunner's Arsenal - Good or Bad?
Note though, this is just my opinion - you're welcome to share yours if you like.

Pulsar
---------------------------------------------------------------------------------------------------
A very popular choice in-game - and I can see why.
The Pulsar's shots make for a good area denial weapon, effectively turning you into a mobile 'bomber'.
The potency of this weapon is amplified with the Kilowatt Pulsar line, as the shock can do wonders with disrupting the enemy's attacks.

NOTE: When using the Pulsar, always try to keep your enemy at the optimum range of the weapon - that is, just when the shot expands. It's tricky, but it pays off when done right.

Advanced Tips
- Take advantage of the exploding shot to manipulate your foes' positions - while blindly firing towards them works, you can fire just to the side of them to knock them towards a hazard right beside them.
- Shots automatically explode after travelling their maximum distance; again don't waste these shots, take advantage of the position where they blow up to reposition your enemies.
- If multiple guardians are camping at a point, you can fire in between them to disperse them, then move in quickly and plant bombs, or push them to a corner and suppress them at that corner to prevent them from recapping the point. However, I do not recommend the latter for long; if you must, have a teammate with a good sword take care of them.
---------------------------------------------------------------------------------------------------
Alchemers
---------------------------------------------------------------------------------------------------
Versatile in many ways - but make sure you upgrade it to at least 3*.
The Alchemer's strength lies in moderately fast bullets and decent dps - particularly at later levels when the bullets break off more.
With elemental Alchemers, you can be an efficient disruptor/dps without the hindrance of slow bullet speeds. Personally I have no preference for the elemental ones, as they all seem to do their part relatively well.

NOTE: Using the Prismatech/Shadowtech lines effectively limits you to a dps role.

Advanced Tips
- 3* Alchemers and above have bullets that ricochet randomly to the left.
- The Charge Attack splits into normal bullets at about 45 degrees from the left and right of the original trajectory, flying back to the player. This makes the shots more predictable than the normal shot.
- If aiming fails, try to lure enemies into a corridor and fire at the wall - hopefully your ricochets will bank off the wall and hit the target.
- Position yourself so that the ricochets hit as many enemies as possible.
- The trick about this gun is unpredictability - smarter players will shy away from these as they will not know if the ricochets will hit them for massive damage.

- Firotech Alchemer: Proc your shots carefully - generally I would try switching to another weapon once your target is on fire, or in the rare case where you are going up against several opponents, try to set others on fire once you've done the same for the first target.
- Cryotech Alchemer: This weapon pairs very well with sword users, as you can unleash a powerful charge attack from behind (not recommended when there are multiple opponents). The optimum time to do so is when they have just escaped the freeze effect, however note that strikers may dash away if you are not fast enough.
- Voltech Alchemer: Shock makes for an effective disruption status, and taking advantage of the small window of time when the opponent spasms can vastly increase your damage output with relatively little risk. This is particularly useful on strikers, as the spasms make targeting them much easier.
---------------------------------------------------------------------------------------------------
Autogun
---------------------------------------------------------------------------------------------------
Another popular choice among gunners, though personally I do not recommend this.
The fact that the Autogun forces you to stay still to shoot turns you into a sitting duck for enemy players - ESPECIALLY gunners. Once you've pointed your gun, it's fairly easy for anyone to dodge you unless you're firing on a narrow corridor. In fact, I recommend you only use this along narrow corridors.
If anything, the only uses for this gun would be to spot cloaked recons or to deliver the coupe de grace on weak enemy players, but seriously, you're better off with a sword.

Oh, and if you must get an Autogun, don't get the Toxic Needle. Poison is a debuff that you don't particularly need in LD.

NOTE: Charge attacks will leave you extremely vulnerable, so do not use them.

Advanced Tips
- The Charge Attack fires 15 bullets in a sweeping motion 7 squares wide - 2 squares wider than the normal shot.
- The Needle Shot's attacks do not pull your enemy towards you.
- For people with very bad latency, this can be decent in spotting Recons - but I do not recommend this for offensive play as the damage per shot is very minimal.
---------------------------------------------------------------------------------------------------
Antigua
---------------------------------------------------------------------------------------------------
A fairly useful gun for PVP, albeit limited to a non-DPS role.
Its primary advantage lies in the fact that it has 6 rounds in a clip - use this to lay down a barrage of shots and scare off attackers.
Advanced Tips
- Staggering your shots so that temporary invulnerability wears off gives you optimum DPS, especially since you don't need to worry about bullet speed.
- Alternatively, fire 5 shots in quick succession to area-cancel.
- The upgrade line you choose for this gun is irrelevant, although if you are a serious PVP gunner you can opt for Sentenza since less players have strong shadow defence; in contrast elemental defence equipments are plentiful in-game.
- If possible, do not use the Charge Attack - the temporary invulnerability negates your final shot that deals far more damage. Otherwise, try to position yourself so that only the final shot lands; this is a difficult tactic especially for enemies that don't move in a straight line; i.e. almost anyone.
---------------------------------------------------------------------------------------------------
Catalyzer
---------------------------------------------------------------------------------------------------
I personally do not recommend this.
The weapon's rounds are even slower than the Pulsar - and that says a lot.
Worse still, it's main power lies in its charge attack, which can be very difficult to pull off. Sure, the idea of blowing up several high-damage charges sounds tantalising, but remember that the projectile speed is terrible, so landing one of these charges on an enemy is already a feat, nevermind blowing it up.
The Toxic Catalyzer line doesn't seem to help much either. Poison is a pretty bad disable in LD; if anything it lowers the damage of the enemy, and that's that. But the damage done by Fire/Shock/Freeze would certainly be much more potent.

Advanced Tips
- Close-range striking seems to work moderately well with this gun, although caution must be taken to avoid getting hit. Get close enough so that you can land the charge shot with ease, but not close enough to get hit by the other party's weapon.
- This gun works wonders in breaking up several camping Guardians; however it has limited function besides that.
- Don't get cocky with your charge shots; if you land one, land just one more and fire. Don't be tempted to stack numerous shots; in the end you need just enough to wipe off a fair chunk of their health.
---------------------------------------------------------------------------------------------------
Magnus
---------------------------------------------------------------------------------------------------
This gun is something that requires you to keep your distance - but when played right, it can make killing off a tough guy a lot easier.
However, the "standing still to fire" leaves you extremely vulnerable. 'Nuff said about that.
The bullets stun, and travel at a high speed. When using this gun, you're better off standing far away and becoming a 'sniper' for your team.

NOTE: Never, EVER, use the Charge Attack. Once you're knocked down, you're essentially dead.

Advanced Tips
- If you attempt to get up close with this gun, always carry a sword with you. The stun/slash combination is potent (kudos to a T2 gunner, of whom I have forgotten your name - my bad!), so long as you are capable of sidestepping incoming attacks. Also, never use this against a group of enemies.
- Try sniping a striker or a guardian before your teammates attack him; you'll save the team a lot of trouble, especially if they are not particularly adept at dodging strikes. And don't worry about dodging; chances are the bullet's so fast that enemies will have a hard time avoiding it.
---------------------------------------------------------------------------------------------------
Blaster
---------------------------------------------------------------------------------------------------
If you have one of these guns on you, I seriously question your sense of judgement.
That being said, you won't really get anywhere with this one.
Firstly - normal damage. I.e. the most pathetic damage of all guns.
Then there's the debuff - oh wait, there's none, save for an itty bitty knockback upon bullet impact.

tl;dr, if you are using one, I sincerely hope it's only to taunt the enemy team, and not as a serious gunner loadout.

Advanced Tips
- You're joking right? Advanced tips for THIS gun?
---------------------------------------------------------------------------------------------------