I recommend getting an elemental AND a shadow weapon, it'll cover all your bases for the most part. Piercing is luxury if you have issues with them and don't have an alternative.

Well i haven't use anything except Glacius from Brandish line but i can say this. IT'S AWESOME!! You don't see a point of freeze? 2 words-Crowd Control.
My favorite thing is to freeze a bunch of enemyes in place, get behind them, wait for ice to melt(on t3 they get 200+ dmg when ice breaks) and chop the crap out of them till they turn arround.
If you time the charge right, it interupts any atack/cast. That means you can get in gun pupys face and stop it a second before it shoots. 1 more hit and its down.
Glacius is epic against undeads/mecha becouse its elemental , but it's really weak against gremlins/beasts. It can get really annoying when you have to kill healers (gremlins) but hey, who doesen't like the chalenge.
If you are aiming for Glacius, my advice is for you to save money and get CTR high or very high. Becouse when yor weapon hits lvl 10 heat, youll have Maximum or Ultra CTR. So that means you'll spam charge atack and that's ownage :D
And also, Glacius is awesome team weapon. If properly used it's good as any ice bomb. I got a friend with Divine Avanger, and mobs can't even come near us. He knocks them back i frost them in place. Till charge is up again, ice breaks(they take +dmg) And repeat.
Sooo, that's about it :)
Sorry for borring you with this but i can't say how much im pleased with this weapon.

The point of Glacius is that you do a charge attack, heavily damaging and freezing half the enemies in the room. You proceed to butcher whatever didn't get frozen. Everything that was frozen, unfreezes and takes about as much damage as the charge attack did, then you mop them up. If you do it all right, staying calm and careful and.. dare I say... "chill"... then you take out mobs effortlessly.

Combuster is a bit different. You ignite half the enemies in the room with STRONG fire, and then either walk away and let them burn or start chopping to make them die a bit faster. It's very aggressive, results in lots of monsters dead quickly, but doesn't offer you any sort of protection during that.

Acheron is... well, it's for when you just want a no-frills sword that does dark damage. And looks like a katana. I guess it being a katana would be a bonus for people who are into that sort of thing, right?

Ignore the Cautery Sword comment... That alchemy line only goes up to that. No 4- or 5-star recipes.

Glacius and Combuster only cause status effects on their charge attacks if I'm not mistaken. Most of the time, swordsmen tend to just use the standard weapon combos. I must say, unless you -really- want a sword to incinerate or freeze enemies (the Alchemer series of handguns do that job much better I believe) or prefer the quick three-hit style of these types of weapons, go for a different elemental weapon.

Acheron, on the other hand, I believe pretty good. Think of it as a faster Gran Faust minus the ability to curse. The fact that most swordsmen don't charge for their attacks for the most part isn't missed since there's no status effect to this weapon. And it eats up one of the most annoying types of enemies- Gremlins.

The reason I use my Iceburst Brandish (Haven't found the stupid recipe for the next level yet), is I get approx. the same burst and dmg. from it that I'd get out of a similarly-priced bomb, with the added bonus that I can hit things with it when things are up close in my face. When you only have 2 slots and are unwilling to spring for a slot upgrade, that combination of bomb and sword is key.

@ ShideKnight: Why use a sword for CC?

1. Glacius' freeze is VERY dependable. It happens most of the time that you do a charge attack, and never when you don't do a charge attack, so you have complete control. With Cryo-drivers, you have to keep blasting away until it does eventually happen... ... and then accidentally unfreeze them when another bullet hits. Especially if you're charge-shotting into a group.

2. It's controllable in a different way. Sometimes you only want to freeze one thing (and maybe a random second nearby thing) and a gun is fine for that. Sometimes you want to freeze everything. But sometimes, you WANT to only freeze half of the monsters so that you can lure the rest AWAY from the frozen ones and attack them. Glacius is perfect for that.

2. The different strengths of freeze do greatly different amounts of damage if you let them thaw out on their own. With minor freeze (such as on the shivermist line bombs) you really SHOULD hit them with ANYTHING before they unfreeze. With medium freeze (such as on the cryo guns) you're still probably better off hitting them with a decent attack unless you really only care about the CC (in which case you should just go for the bomb) ... But with STRONG freeze? I am seriously NOT EXAGGERATING when I say the de-thaw causes them as much damage as the entire charge attack itself. It is massive. It usually finishes off the weaker enemies. It does normal damage (I think) so even if you hit a gremlin or beast with that Glacius the freeze is going to hurt them.

Seriously. If you see someone freeze a monster with a Glacius, don't you dare hit that monster with anything less than a really good charged attack. I'm not even kidding. It doesn't help to interrupt my multiple-hundred-damage de-freeze with a single almost-hundred of sword.

@ Soulfeast: Or you could get one of those big, hard-hitting, slow bombs and time it so that it goes off right after the monsters de-thaw. Mwahaha. Also, I've been told that the non-damaging charges from the new Catalyzer guns do NOT break freeze, which means you could hit them with the sword and then sit there attaching catalyzer charges one after the other all over the monster, with them helpless to avoid, and then blow them up after they de-thaw. >:D