Who are your favorite obscure/underused villains? Spider-Man and Batman alone have enough z-list villains to fill several rogue's galleries.

I'm fond of the Superior Foes team, naturally. It made great use of a throwaway Slott character (Overdrive), a throwaway Brubaker character (Beetle) and a bunch of established spidey villains. Pretty much the perfect way to use that kind of villain, I think.