The Rocket-Powered Skateboard is an item that has the ability to use a jet turbine that is attacthed to it's back end to blast away. The item could've orignally been owned by Roostre. Though, he could've grabbed it out of Mouse's purple bag in "Adventure Mouse."
Season 1: 
In its first appearance, it was being used by Roostre to skate around his shack as Fitz was escaping from the New Guy. It was also used in the episode by Fitz, Skillet and the New Guy as they blasted around the desert, when they tried to arrive at Shark's party.
The skateboard appears again in "Surgery Circus" when Fitz, Skillet, New Guy and the Eye escape Rhoda's Bar. The item appears again when Fitz, Skillet, New Guy and the Eye are traveling through the desert, as they head to Liquor's shop so they can re-attach the eye's leg.
The item also appeared in the episode "Booger Haze" when Fitz and Skillet headed to Roostre's shack and they had to fill it up with gas first. Though, instead of just getting the gas for the so-called vehicle, they just blew up the gas station instead.