The Pimp Suit is a special outfit in GTA San Andreas. It is a blue suit with a white frilly shirt, a dollar necklace and platform shoes. The outfit is given to CJ after attaining a 100% relationship level with Denise. There is no purpose for it and it isn't necessary for Pimping Missions.
A pimp named Jizzy B is seen wearing a suit like this in the game. However, unlike CJ, his suit is purple.