Cripes, where do I start? Have random list. All readily googlable and I'm too lazy to do links.
Age of Pirates 2: Gentlemen of Fortune mod
Any Total War Series except Rome 2 - google Darthmod...profit.
Rome 2: Radeous mod
Mount My Blade - Floris Mod Pack is pretty much everything but there are other good ones out. Taleworlds forum is comprehensive.
Freespace 2 Open plus all the mods (Get FS2 GOG versionthen use this:
http://www.hard-light.net/wiki/index.ph ... _Installer). Blue Planet is a great campaign. MP works fine but you can't save missions in progress, so don't die.
Silent Hunter IV (fuck V) - RFB, RSRDC, NMMO - these will mean something to you if you care to start googlage.
Falcon 4 BMS - still by far the definitive MP flightsim experience bar none (yes I'm looking at you DCS) in all it's DX9 glory. Amazingly easy on the eye for a 16 year old game. I still play this in MP at least twice a week.
System Shock 2 Rebirth + SHTUP (Texture Upgrade Project) - I've yet to find anyone willing to see this through to the end in coop. It actually requires effort compared to modern games.
X3 Series (ignore Afterbirth, just pretend it never happened) - very good list on Egosoft forums
Now you know what kind of games I enjoy I fully expect most 5punkers to completely ignore this list and move on to the BF1942 mods...
