Black Shell

Mario Kart Arcade GP Series
Black Shells are shells of unknown origin that appear in the Mario Kart GP series. Its effects are similar to that of a Winged Spiny Shell, though unlike a Winged Spiny Shell, it can only be fired straight and has a higher appearance rate. They explode upon impact of a wall, obstacle, or other racer, sending those caught in the blast soaring for a second. They can also be used as a triple if unlocked.

Other forms of media
The shells of a Bombshell Koopa are black, and explode. Some evidently high-ranking members of the Koopa Troop, such as some Fire Bros., Black Ninjakoopa, and Lakithunder, are shown to wear non-exploding Black Shells. Additionally, in The Super Mario Bros. Super Show! Koopa Troopas, Lakitus, and Hammer Brothers were portrayed as wearing, as the episode "Mario and Joliet" showed, fire-proof Black Shells.

Trivia

 * The Black Pac-Bomb in Pac-Man World Rally is similar to the Black Shell. This is the same with the Green Shell, Red Shell, and Blue Shell, which are all similar to their respective Pac-Bomb companions.