The Contestant Cannon is an object in Object Overload and it's reboot.
The cannon is a fuseless cannon only activated by a button, as shown in the first episode of the original and reboot versions. The cannon's body is light-gray, with a red and yellow explosion design on it. In The End of the Beginning, it's stands were dark red, but in the later original episodes, it has brown stands, and in the reboot, it has red stands and has gained a fuse.
The cannon was first seen in The End of the Beginning, hidden under a cloth pulled by Gamey. It was used to send all the armless contestants (with the exception of Ping Pong Ball) to their podiums.
The cannon is not seen again until episode 3, where it is shown that it is used for eliminations as part of the method to send someone to Prison Planet: once the Sender Scoop Thrower flings the eliminated contestant into the cannon, it shoots the contestant up into space.
This isn't the only use it has after episode 1: in Branching Out, Ping Pong Ball suggests that his team, Team Tune, should launch their team member to the top with the cannon. Disc was chosen to be shot out by PPB's team's leader, Boombox (because she thought he was a frisbee), and Soccer Ball and Masky were sent to get the cannon.
Locky notices that Team Tune has the cannon, which is being held by Soccer Ball and Masky. Soccer Ball says "fire!," which causes the cannon to shoot a cannonball (showing that contestants aren't just shot out of the cannon and that there is another method of making the cannon fire what's inside it). However, the plan failed as Disc shattered.
The cannon returns in Rostrum Rampage, the first episode of the reboot, as Gamey pulls the cover over it off. It was once again used to send the armless contestants to the podiums.