Shadow (pure SS and melee)
Justicar (Bubble dropping up close)
Valkyrie (Adrenaline pumped up-in-their-face-class)
Juggy (Force Choke + ragdolling ftw)
Human Adept (Powers, Acolyte and Heavy Melee - even more ragdolling)
Batarian Slasher (mook catapultation and cluster big booms)
Asari Vanguard (the B52 of Vanguards)
Fury (Detonations on host, cute LM)
Kroguard (for real melee action)
KroSent (for even more melee action with a hammer)
Batguard (melee action with hatesurf potential)
Cabal (staggering LM against all the phantoms)
AIU (best footjob in the game)
Electra (supreme CC domination with shock drone and triple electroshocks, fire explosions as well)
Paladin (the riot police are here and they're angry - bash all the things, explode all the stuff - consider yourself under arrest!)
Havoc (can't make the Reegar work with the short range? - get close with Havoc and laugh)
Huntress (for lazy times)
Geth Trooper (Spitfire barrage - even better than on Juggy)
TSol (for testing out what can be done with guns)
BatSol (Hatesurf+stagger and firebombs - what's not to like here?)
Demolisher (when I get annoyed I chuck grenades and use my harrier)
MQI (when I feel like Plat)
The other ones I don't play as often, but a Volus Sent in a geth match is also fun.