The Carcer City Unicorns is a sports team from Carcer City. Pedestrians in Grand Theft Auto IV can be seen wearing clothing emblazoned with the team's logo. It is unknown what sport the Unicorns play. The Unicorns might be based on Detroit Lions, as the Unicorns' logo looks similar to the Lions.
It can be assumed that it is a basketball team, as the logo is usually on a basketball shirt worn by pedestrians.