Imagine Everyone's Mortal But Me with deadly sniper seats... A grenade from the hill into any sniper seat will make life very uncomfortable for anyone in there, whether the grenade hits near them or not. A pretty fun secret that will never be seen by folks not using custom physics models (like the one enclosed).
Another unique concept in team Marathon. Using the enclosed physics model, you'll be able to shoot the skull at one of two speeds-one for passing, one for shooting on goal. There's a small room off to one side with two sets of 4 switches... you throw one from your set when you score. The first team to 4 wins. Try it!
Inspired by the M1 map Chunnel. The object is to flip the switch in your opponent's base. (Similar to, but still different from, the Assault! concept.) Very nice layout. Size comes from a sound file the author uses to describe the map.