I was always a fan of the Thor (Summoner), heavier armament but still mobile... I rarely used anything heavier than that if I could avoid it. Used to strip it and pack on as much Ultra AC or LBX as I could. I liked being able to run in, hammer the crap out of the enemy and not really have to worry about overheating.
Conversely, my buddy's fave setup of all time was a Daishi with nothing but ER Large Lasers and heatsinks. He called it the Iron Knuckle. One shot, and it overheated, but pretty much anything short of an Atlas was dead if that shot landed, and even heavier mechs would take so much damage it would buy him time to recover from the overheat.