From the Super Mario Wiki
The Wario Grab is a grab that Wario can execute in his various games. When near an off-balance enemy, the player must grab and hold the B button to pick the enemy up (in handheld games, Wario does this automatically). In handheld games, the player must press the B button to throw the enemy. In Wario World, many special moves can be done with this maneuver, including the Mega Toss, Piledriver, and Wild Swing-Ding.