Step One: Steal your friends phone and run into the other room(don't let them know)
Step Two: Go into their contacts and pick someone embarrassing
Step Three: While it's ringing, run to your friend and hand them their phone.
This will cause them to act like an idiot while they try to answer their phone, or if no one answers, while the person calls your friend back and has to explain what happened.
Kellen- phone grenade!
Bill- uh,uh,uh what?
the act of taking your friends phone, dialing their ex-girlfriend/boyfriend's number, then tossing it to them as it rings. Usually results in the "victim" of the grenade having a very awkward, yet hilarious exchange with their ex.
Me: Hey Nick! Catch!'
Nick: DAMNIT!...I mean...um hey Julie
Julie: Why the hell are you calling me?
Nick: Sorry I got phone grenaded.