For me it's Aerowalk By Hubster, SiMetrik By Sock & Black Town By XPac. The three best maps I've played really I loved everything about them. Spent constant hours playing on those maps I'm surprised SiMetrik hasn't even made it to Quake Live yet honestly it's well worth it!

Edited 11.2 minutes after the original posting.

You can find Aerowalk and SiMetrik on the AKUTA server. Enjoy =]

Edited 4.46 hours after the original posting.

Personally, I wouldn't realise use custom maps on my server. I'd just use the originals because some files may take time for the people who want to join the server to download and sometimes it may not even download meaning people will leave. But it's your server so Good Luck!

Well, FT. I think people that come to Q3 new will play original baseq3 rotation with satisfaction, but people who played every default arena in the game many times will gladly wait for download or gladly will download defined rotation on them own from given link. Note that people who are new to Q3 are counting down and people will be pleased by every new map that is good-rated by community and forced to download it and play eighter offline or online. Q3 servers are one by one shutting down, amount of them is counting down pretty quickly, reffering to QL. Newly created servers run old outdated versions which are not compatible with version of most people, the last one developer - 1.32c is mostly used by people offline playing with bots, but if I take AKUTA server that runs NoGhost server on version 1.15c - without version switcher I have no chance to play it. I downloaded NG mod for 1.32+ and it is really a bit bugy. Last I realised glitch that sent my look camera to the void when respawned (my model stayed in the map)...

For me it is charon.
Good balance between gameplay, visuals and bots. I remember the excitement every time charon came with a new map. And his geo-maps for the competitions by nunuk/sparth stood out in their own way.
I also like DruZli, d3xf1 and d3xf2 are amazing in their gameplay.
And mappers like bal, lunaran, tequila, killer and stormshadow are high on my fav. list... I think thre are a lot more mappers that should be mentioned here, the q3 community have and had some amazingly talented mappers building maps for it...