The infinity level, ported to the M2 alien textures. It's no longer vacuum, and all the baddies are gone... but so are some of the windows (which makes for easy transfer from hallway to hallway, actually).
A multi-tiered level based on the concept of a box canyon. There are no indications for the elevators... you just have to know where they are. Seemed really, really low on ammo, as well...
A funky little wide open 5D map with edges so sharp I'd hesitate to try this on an 040 machine. However, it plays beautifully on a PPC... you won't be getting too many wall kills on this one.