The Clamboni is a device used to clean ice rinks. Mr. Krabs uses it to give kids rides. It only appears in the episode "Krabs à la Mode."
It is a large green vehicle with a paper sign reading "Ride $1" in red writing on the side, stuck on by sticky tape. There is a yellow seat atop the vehicle accompanied by multiple levers and a steering wheel. There is a vent on the back of the vehicle; presumably a radiator.
The clamboni is first seen being driven by Mr. Krabs, who is giving rides to multiple children. Later in the episode, Plankton tries to use it as a means of escape after obtaining a Krabby Patty, using the clamboni to run into SpongeBob, Squidward, and the Bikini Bottom Hockey Team while Patrick has his tongue stuck to the clamboni's rear. This causes the Krusty Krab's entrance to be blocked, causing the clamboni to stop. The clamboni then breaks down, to Plankton's lament.