The B button is the small, red button on the GameCube controller, the large, green button on the Nintendo 64 controller, the rectangular trigger on the back of the Wii remote, or the small, clear button towards the bottom right of the Classic controller. It is used to activate special moves in SSB and SSBM. In SSBB, it activates normal moves on the Classic setup, while on the Wii remote, the B button activates the shield move.