Yeah, so, ok - re read "Making Money" and couldn't help myself.
Basic system: Players each (funniest, as determined by previous round, first) build up the situation, adding things ot be used and antagonists. "In a darkened warehouse" "Ninjas sneak fearfully"
Then they beat the snot out of them as only Groucho can.
Not entirely sure on how to adjudicate this. Perhaps something wager based. Or maybe just go apples-style and not care about winners.
Also tempted to use random cards for the characters and antagonists.
I do have a silly setting though. Aliens land and decide to integrate the very best of human culture. So they run a tournament to see are the more fatal.
Blegh, this was funnyier at 4am. Ah well, consigned to the /BadIdeas bin.
Pallando adds: See also MontyPython's KillingJoke?, DrWho's GreatestShowInTheGalaxy? and the Nobilis combat system in which protecting against an atomic bomb is low level stuff, but it takes really high level skill points to protect against satire.