Prisoners of the Tower
A very complicated map, with lots and lots and lots of secrets. Too many slow-moving elevators for my taste, but if you're willing to take the time to get to know this map, you will find that there are a myriad of ways to kill your friends. As the author says, "the map is your weapon."
Levels in map "Prisoners of the Tower":
Prisoners of the Tower by Daniel Loebl