Thinking of a pistol again, it must be CO2, fun, reliable, multi shot, relatively accurate and probably BB. It's only for informal plinking, A decent shot count would be nice, so no blow backs, I'm thinking possibly a revolver. I confess I don't know a great deal about these type of pistols, so suggestions please chaps

Edit: It will be secondhand, as are all my guns and wanting something under £100.