Darkimmortal's crazy Prop Hunt mod for Team Fortress 2 has been out for a little while, but somehow eluded us until now. Thanks to the below video, we can safely say this is something worth checking out.
The setup is simple: one team spawns as Team Fortress 2 props and scurries to hide, while the other all-Pyro team must seek out and identify those props from the rest of the scenery. It all results in some fairly hilarious situations, such as the sequence beginning at 4:25.
More info on the mod, and servers where it's being played, can be found in the Steam forum thread. Thanks to fullbright for the link.