Leon (I call him Gaston):
-Tongue grab
-Backstab blade
-Cloaking
-Cloak attk. bonus (the masquerade emblem)
-Movement speed
-Dummy upgrades
Sorry, haven't played enough to know all the real names.
One thing I will say is that we absolutely MUST have a Voltar for clan battles. There's no HP regen for the most part so you have to really on either him or going far away in order to get back in the game. His healing is also very fast which means an almost instant regen.
The monkey is also a very good stationary blockade. With a row of mines down, he's pretty hard to get to especially if he has upgraded his laser. That thing is friggin' overkill in the right hands. I couldn't get him down in the one game I played with him, but all the teammates who used him dominated. The best way to take him out is to use Leon's tongue grab. Once he's on the ground you pretty much have him.
DO NOT PUT YOUR BACK TO LEON.
Also you guys might find this blog intredasting:
http://joostdevblog.blogspot.com/2012_03_01_archive.html