When Banjo is by himself and has the Pack Whack, jump in the air and press B to use the move. Quickly after pressing B, jump again, and Banjo will perform a double jump. This is useful for reaching Taxi Pack easily and also for navigating the boxes in Grunty Idustries. It won't save you from high falls though, even if you use it before hitting the ground--but it is fun to watch Banjo get hurt from a seemingly short hop.