Here's an adventure idea for you, based on a campaign of mine featuring the IAD officer from the preceding page.  Have one of your players play an undercover cop in your group, investigating the group itself.  No matter what you do, do not let your other players know of the true nature of the character, generate 2 separate character sheets if necessary, letting him play the false character as his cover identity, the GM keeping the other hidden.  See if the other players can figure out what's happening before they are busted.  Let the adventure go on, letting the characters feel more and more at ease with the cop, running solo games with him to cover his time spent reporting in, and morality issues.  This is quite possibly the dirtiest trick I have ever played on my players, and when they first realized what happened they hated me with every inch of their being, then moments later they realized it was one of the best games I had ever run, all due to implementing the simple idea of playing one character against the rest in a very underhanded way.  In my game, it was an IAD officer investigating a C-SWAT team (player group A) that led to another group deeply imbedded in organized crime (group B).  I came to head just before the officer was about to make his bust, the players figured out what was happening and a 48 hour gaming session ensued with the cop running for his life, after one monumentous running gun battle in which 4 of the 12 characters will killed, and 5 were arrested, 2 disappeared and culminated with the undercover cop and the character who had thought the cop was his best friend, after a drawn out fight on the roof of a building, killed each other.

Now while for me it started out as an IAD cop investigating a C-SWAT team.  This type of game can work just as well with a regular group, simply putting an undercover cop in with your group, and keeping it a secret that only you the GM, and the player controlling the cop know.

For details of the actual adventure itself e-mail me.

(Written by Deric Bernier, conceived by Deric Bernier and Tim Covell.)