BattleBlock theater

you get heads or weapons from the game which you unlock with in game credits
im not sure if anyone would buy the items since they can easily be obtained just by playing the game

Nope. All of them are not worth much and you don't get random drops

Make money... Not so likely.

Fund a missing trading card or two? Yeah, maybe. :)

well... i sold a couple of heads and obatined 6 cents... so no. but the game is fun, pure fun.