A huge open arena, with raised corners, a central sewage pillar (for climbing), and some outside passageways. Probably better with larger groups. Unmerged.
A target practice map. You get lots of weapons and ammo, and access to a circular arena - you can let any number of any kind of nasty in that you want, via a set of (protected) switches. Sorta fun to try and get the jugs to wipe everything else out... Unmerged.