Bullet Bill

Though not exactly an actual species, Bullet Bills are mechanical menaces that are extremely annoying.

In the game Mario Kart DS, part of the Mario Kart sub-series of the Mario universe, you can pick up a Bullet Bill as an item. After activating the Bullet Bill you will morph into one of these large, bullet-shapped creatures and rocket automatically down the track, knocking over any enemies or projectiles in your way. The Bullet Bill is unquestionably one of the best items in the Mario Kart series.