Shock Baton Gag Gift
A little baton that can be used to shock your buddies. Tell people it's a flashlight and let them shock themselves!
It actually works as a flashlight, albeit not a great one. It's not something you're going to use to find burglars in your house - or to stun them with (it doesn't pack a wallop, just a small spark).
But that makes it even better as you and your friends can continually mess with each other while watching the ball game. :p