Spin
The Star Spin is a move that Mario can perform in Super Mario Galaxy. It is done when the player shakes the Wii Remote or Nunchuk for left-handed Players. The move is slightly like a Spin Jump or Mario Tornado except that it is done on the ground. It can be used to reflect projectiles flying at Mario, stun enemies, activate switches, swim faster, do a higher jump, and even pick up nearby items!
Mario is able to do a Star Spin because of Luma, a white Luma given to Mario by Princess Rosalina. Whenever Mario does a Star Spin, Luma pops out of his hat for a second. Interestingly, whenever Mario does a Star Spin, Luigi and all nearby Lumas and Toads react to it.
A extremely useful application of the Star Spin is the ability to stun, freeze, or make enemies dizzy by spinning into them. This gives Mario a chance to escape or attack the enemies if the Player is fast enough.