Garrys Mod 13 Mod Spotlight - GMod Tower

http://www.gmtower.org/
http://www.youtube.com/FlippingWes
http://www.youtube.com/AWJETS

Essentially, the server (or tower) acts as a base for all the gamemodes it contains. You are not limited to one type of gameplay. The community forms what makes the tower interesting and the community controls how it's ran.

In the tower, you will have access to personal suites, stores, a whole batch of unique gamemodes, and much more.

There are plenty of well-thoughtout features/systems for your convenience. Trading (including currency exchange), grouping, gamemode queuing, awards (similar to achievements), and hand-picked administrators, just to name a few.