Heimer is probably the strongest I've run across. I played him a while this weekend and the only champ that could really counter me was Kog. Everyone else I could out-harass and push. Once on a point it takes very fast burst by 2-3 people to take me down. (I love having 2 turrets up, ult, missiles, grenade stunning someone, as the other 2 people charge me, zhonya's while the turrets + turret kill them, and kiting with exhaust until they die).
As heimer I have out-pushed and held against virtually every champion in this thread, many times 2 of them by myself.