I love Timber Wolf, 75 tons of lasers and long-range missiles. Clan mechs didn't seem overpowered in MW2 because you were fighting clanmechs--and elementals on one mission, those are impossible to hit.
Urban Mech, 35 tons I think? I think they are decent at urban combat.
It didn't have many guns, didn't have much armor, couldn't shoot that far, and couldn't run that far. Still, I managed to evade and shoot intelligently. When I thought I was going to die I rammed a mech off a cliff, survived, and killed him. And then I got sniped, fell over, did some damage, and finally died.
My next one was a medium mech, and much, much better. I can't remember what the 'game mode' was, but it was fun as hell and I really am considering getting into it.