Ripcord
This is one big map. Some nice lighting effects, and sound is used well... but with fewer than about four, you'll feel lost. Textures are nicely spread out... you can pretty well place yourself by the walls around you. (This is a good thing, on a map this big...) A few nice secrets, for those with the time to find them.
Levels in map "Ripcord":
Noble's Noggin