You know, I really ought to try Infiltrator and Soldier. Everyone seems to rave about them, but I've never been a huge fan of the tech powers, and like my biotics too much. That means I don't generally get to use the sniper rifle, though, which sounds like fun to me. It's been a pet wish of mine that they bump up the tech powers to be more tempting in ME3. They just never looked that interesting to me. I ought to play through again to try them out.

Adept with an assault rifle. 
 
It makes you feel like a space wizard. 
 
EDIT: Although the Infiltrator is a close second.

Mine is Dinosaurian World or Japanese History. Maybe Life in Italy and China during the Renaissance. Oh wait. You meant battle class. Ha! My bad.

having adrenelin rush and that fucking widow sniper rifle with full disruptor or incinerator ammo = 1 shot kills on hardened. or at least disabling shields and biotic barriers and letting the teammates do the rest.