A rather infamous power-up, Kuribo's Shoe is basically a character-sized wind-up shoe in Super Mario Brothers 3 (an NES game, recently ported to GBA). Found in world 5 area 3, it's frequently ridden by Goombas (or Kuribos, as they're known in the Japanese version; hence the shoe's rather odd name), and is a pain to get off of them without getting rid of the shoe in the process. Upon comandeering one of these shoes from an unlucky Goomba, the player suddenly finds themselves in a bouncing shoe that nothing can damage, and any enemy that touches it dies. The only things that pose any threat to the player are falling into pits and having time run out. In essence, Kuribo's Shoe is an all-but-endless invincibility power-up.
"Oh shit! I got the shoe! I'm so invincible! Oh! Eat it, you bitch! You don't understand! I got the damn SHOE! It's the shoe! And look at how cute I am with my stupid plumber head poking out of the wind up sock! I am the cutest invincible shoe rider ever! Mario! Mario! He's in the ULTRA green SHOOEEE!" - Seanbaby, on Kuribo's Shoe