Application Outgoing Incomming Notes
Aliens vs Predator 80, 2300-2400, 8000-8999 Beware, lots of ports open!
Asherons Call *** 9000-9013 *** May need to open MSN-DX and/or MSN Gamezone ports
Black and White 2611-2612, 6500, 6667, 27900
Dark Reign 2 3100, 3568, 3999 3100, 3568, 3999
Delta Force, Land Warrior 17478 17478(?) perhaphs DMZ
Dune 2000 1140-1234, 4000 1140-1234, 4000
Elite Force 26000, 27500, 27910, 27960 
Everquest 1024-6000, 7000 Beware, lots of ports open!
F-22 Lightning 3 4533-4660
Fighter Ace II 50000-51000
Fighter Ace II DX 2300-2400, 47624, 50000-50100
Ghost Recon/Ghost Recon Desert Siege: 2346, 2347, and 2348 2346, 2347, and 2348  TCP and UDP
Half Life 27015
Hexen II 26900 (+1) each player needs their own port.  Increment by one for each person
Heritic II 28910
KALI 2213(+1),  6666 each computer needs their own port.  Increment by one for each person
MSN Gaming Zone 6667, 28800-29000 Lots of ports, beware
MSN Gaming Zone - DX 2300-2400, 47624
Myth 3453
Need for Speed 9442
Need for Speed 3 1030
Outlaws 5310
Quake I DMZ
Quake II 27910
Quake III 27960 (+1) each computer needs their own port.  Increment by one for each person
Rainbow 6 2346 2346
Rogue Spear 2346 2436
Starcraft 6112
Tiberian Sun 1140-1234, 4000 1140-1234, 4000
Ultima 5001-5010 game; 7775-7777 login; 8888-9999 patch; 8800-8900 messenger; 7875 monitor yikes!
GameSpy Arcade Config
GameSpy has a bunch of services that all require a special port.  Here is a list of GameSpy ports and their related services
Application Outgoing Incomming Notes
IRC 6667
Voice Chat Port 3783
Master Server UDP Heartbeat 27900
Master Server List Request 28900
GP Connection Manager 29900
GP Search Manager 29901
Custom UDP Pings 13139
Dplay UDP 6515