Gunzerker, went with the rampage tree first. Gunzerkering class ability basically makes badasses into normal enemies in terms of difficulty. On the flipside i'm not using it as frequently as other classes use theirs.
Same here. I've been enjoying the Gunzerking quite a bit. Been investing points into making my rampages last longer to off-set to long-ish cooldown. Also, big magazines are a must. Reloading is so slow.
Playing in co-op with a Commando and a Siren has been pretty great. Having a friend lock down enemies with phase lock while I gunzerk them has made some elites almost pushovers.