Vexing Radgull is a uncommon Creature — Bird Mutant card from Fallout (PIP), collector number 41. Current market price: $0.90 (foil $9.51), TCGplayer market prices via Scryfall.
Flying Whenever this creature deals combat damage to a player, that player gets two rad counters if they don't have any rad counters. Otherwise, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)