Rubber dinghy rapids, bro!
and then get arrested under anti-terrorism legislation, detained without trial and possibly sentenced for serious crimes. they take that kind of stuff pretty seriously over here, and I'm sure they're even more jumpy about it in the states.Call the FBI hotline and say: "I know who you are. if you don't give me the money, I will hunt you. I will find you. And I will kill you.".
incidentally, prank calling is juvenile and unfunny. leave it to the professionals.