The Thought Cannon Wand is a giant wand which Finn and Jake stole from a wizard after beating him. After stealing it, they planned to dig a hole in front of the tree fort and bury it as they think it's dangerous. When Jake tries to operate the wand, he fails in trying to think of a deeper hole to bury the thought cannon and thinks of a sandwich instead.
In the future, the buried Thought Cannon Wand is found by Cuber and he tries to use it to escape Space Wedding People. He too makes a mistake and a giant sandwich pushes him out of the hole flinging him far away.
The Thought Cannon Wand is a giant wand with a thought cannon (the yellow star) at the end of the stick. It supposedly has the ability to spawn any thing the user thinks of. However, Jake and Cuber both think of the wrong thing and spawn a sandwich.