A small circular killing field, surrounded by an outer ring and filled with just enough stuff to make life interesting. Lots and lots of invisibilities... Pass through the center to kill the lights, pass into (or out of) the outer ring to bring 'em back up. For added fun, the Tempus Choir is replaced by Alvin and the Chipmunks. A fast-paced blast.
A rather convoluted water-filled map, with the rhythm non-trivial to learn... but once you've got it down, this is a pretty cool map for medium to large groups. Lots of secrets, lots of acceptable strategies... nice construction (although on slower machines, it's a dog). Well worth the learning curve.
A tall cylinder, filled with openings and interconnected passageways. Physics allow you to drift... main weapon is the nuke gun, which can lead to some nasty suiciding if you're not careful. See how good you are at shooting on the fly!
A few loops, and a flushable toilet. Lots of ammo, and lots of weapons... high carnage. (Beware the yellow and black assault on your eyes in certain parts of this map...)