You may be looking for No. 1, a mission in Grand Theft Auto IV.
No. 1 (not to be confused with Zero) is a resident of Liberty City in 1998, and is most known for his appearances as a hitman. In the mission No Son of Mine, Ma Cipriani issued a hit on her son, Toni Cipriani, No.1 poses as the hitmen who are searching for Toni. He also appear in Grand Theft Auto: Vice City Stories, posing as hitmen against multiple people. In both editions, No. 1 is a playable multiplayer character.