Crossbows and bows have good range and pierce through multiple monsters. Crossbow is weaker then the bow, but you can move while firing. Bow makes you stand still, but deals good damage+ effects.
I reckon the problem lies with most people not wanting a single-shot gun that requires reloading.
That and a crossbow with an 'extended magazine' sounds silly, and looks silly (believe me, I've designed them before).
Of course, one possible mechanic you can use could be similar to the indie game Bastion; where the bow, for instance is a single-shot weapon that increases in power the longer you draw it (up to a certain point, of course). I have concepts for this; I'll share them another time.

Cluster Bomb keeps foes out of a area for a long while. It uses multiple explosions + lots of Knockback.
Aesthetically... cool! :D Only thing is it might be a bit redundant if enemies are knocked out of the area on the first blast; that being said a large radius bomb would probably be more useful.
On the other hand it does bump up DPS for bombers significantly, and it would be extremely useful in narrow passageways.

Sticky Bomb sticks to foes that get too close, then stay on and explode later, hitting lots of monsters.
Same principle could apply to guns, really (e.g. Catalyzer). Although this would probably be more useful on a projectile weapon, otherwise this is just another proximity mine.

Landmines stay active for ~11 seconds and detonate when a monster gets in range. Single use status bomb or Modern day claymore. Decent damage, stun.
Sounds good, but to balance this and prevent landmine spamming make sure the charge time or the fuse time is long.

Katana... Two swing, first like flourish, second freezes you and target till shield cancel or attack end. Continual damage on second swing. Shadow/Norm OR Pierce/Norm
Makes killing enemies a little too easy... I'd say no. Even with nerfed damage the immobility alone makes it OP.
Alternatively, here's an idea from one of my own threads - basically to make the weapon capable of dodging enemies, and make you move a lot faster.

Lances have a moderate attack speed and a Charge for the charge attack... XD Just using this weapon makes shields awkward. SSD: High, SHD: High, High pierce damage, possibly split with Elemental.
Poke poke! :D Well, it does make a good melee weapon for keeping enemies at range - and just out of their own melee range.

Halberds are a bit lackluster, but deal good damage and have amazing range. Each part of its combo or charge deals either pure Normal, or pure Piercing.
Essentially a longer ranged version of the Troika with the capability to dish out piercing?

Broadswords increase shield stats instead, making shield bearing a much more viable "class". SSI: High, SHI: High, piddly normal damage.
On the condition that they're either slower than a Calibur, or deal slightly less damage.

Claymore (Sword form Scotland) Two swings, dealing more damage then Sealed swords and is faster, but has a heavy toll: SSD: Low and ASI: Med... which makes using ASI less effective. Ele/Norm OR Shadow/Norm. Charge has a Normal damage thrust and a Ele OR Shadow explosion.
Not too keen on a faster SS + Brandish upgrade hybrid, really. Could use a bit more originality.

Like the idea of Shield Health and Shield Speed modifiers, would certainly balance out some of the swords we have; that and place a lot more emphasis on defensive gameplay. Love the ranged weapon ideas; melee may be a bit lackluster, then again there's only so many things you can do with a stabby thing.
Can I have my cookie now? :(

what about axes?

or throwing axes?

or boomerangs/chakrams?

Yay! Update! :D

sniper rifle which can be used first person view for a good shot.
With the wand idea, why don't we have it so certain ones can summon minions.
Oh, and how do you get a face for the forums??

@Earthbound
Sniper rifle? That's not 'knightly' enough for SK. And no to first person too, it just doesn't fit.
And no to summoning minions, that's just a variation of all the pets suggestions.
You want a pic? I knew you new here =P For a pic, click 'Forum Preferences' at the top of this page and then 'Edit'.

@The-rawrcake
So, you mean, basically, a Brandish-Suda hybrid? that could be interesting. +1, although I think a mace would fit in better, you know, it's more sword-like than a flail with its chain...