Marvel's requisite joke hero, Squirrel Girl, is now available in the Marvel Heroes MMO. There's kind of a running gag in the comics that she appears relatively harmless and goofy, but managed to take down Doctor Doom with her legions of squirrel sidekicks. In the game, she can do just that--summon hundreds of fuzzy suburbanite rodents to overwhelm her opposition.
The new update also allows you to unlock the Superior Spider Man costume, from the comics where Dr. Octopus takes over Peter Parker's brain and decides to be a good guy. I think that counts as even sillier than Squirrel Girl.