I am going with game to run at a convention with this one. Hands down, it's All Flesh Must Be Eaten. The players show up expecting to die and hoping they go out in a very cool way.
I have run "Road Trip of the Damned," "The Burning Wheel of Karma," and "Dead Ops" for AFMBE. All three of them give me fond memories.
Not a single one of the memories from RTotD are for polite discussion and they all tend to revolve around the first reveal. You can pick this one up for free at the Eden Studios website.
TBWoK was written by Derek Guder and myself. It involved a flashback, which turned out to be very tricky when one character tried to kill the other during the flashback sequence, and involved a reveal at the end that often ended poorly for over half of the party. This is the only one of the three scenarios not available to the public.
DO was written by James Wilber and is an awesome military with zombies scenario. You can find it in Eden Studios Presents volume two. We use to keep track of how many characters died during this game. We even had one group make a huge mistake after the first reveal and died in the first two hours of the game.