Dod_avalanche. Sniping either from allies window OR the axis doorway in the dark and unseen. Favorite of all time. The most inspiring map to me would probably be De _ Aztec from cs 1.6 or cs _ militia on 1.5. Teaches a lot about volume (geometrically) differences and the importance of line of of sight variations (particularly now that I am more technically minding when creating levels). Starcraft 2 taught me about importance of balance though (started too anyway).
Technically simulated would have been America's Army when it was still 1.X or even 2.X days. That medical training actually came in handy as did the firearms training (clearing a jammed weapon properly). Also, special forces training mission... daaaaaaaaang