Split screen 2-player game ONLY. I recommend JoyToKey to split player control, and then a cardboard divider to split the screen exclusively.
Player left and Player right see a screen of AI crowd members. Each player has 2 bullets. They can collect "Dossiers" to eliminate suspects from the crowd. Once you think you've identified the other player, squeeze the trigger and take 'em out! If you're wrong, well, whoops. The other player might have seen, and they're on your tail! Exciting stealth action for two players!
edit: updated so keyboard controls reflect the correct side of the screen.