Engineer is the truly Heavy buddy. Sure, Medic is amazing, but medic works good with everyone, and best with Demoman due to speed. The new engineer toys, btw, are very good. Maybe too good. Area denial, transport, healing and he still have a shotgun and a pistol with infinite ammo. And if you haven't played it, go try Pl_Frontier. Yes, the map isn't balanced but hell, it's fun and very nice. Play a full round on it at least once, you won't regret it.