Someone in the other thread mentioned mods dont go a long way in making a game what it is. This thread is basically for mods (no maps and skins packs plz) which are complete or under development. So start listing. 
Half Life 2
Garry's Mod
Eclipse mod
The Hidden
Plan of attack
Dystopia *
Black Mesa Source *
Border Patrol *
Adrenaline Gamer
Bloodthirst *
Goldeneye Source *
Citadome
Other mods can be checked Here
Sad that many of the mods originally intended for farcry were cancelled or moved to other engines. Here are some though
Farcry
X-isle 8
Forgotten war
Obsidian Edge *
tacto
Ultraball
Hard
Doom 3
Classic Doom *
Quake 2 lost marine *
Doom Chronicles
Dawn of the dead
Pathways redux
doom 3 jedi *
*= promising mods unless they are canned ofcourse
Keep adding

Half Life 2
Garry's Mod
Eclipse mod
The Hidden
Plan of attack
Dystopia *
Black Mesa Source *
Border Patrol *
Adrenaline Gamer
Bloodthirst *
Goldeneye Source *
Citadome
Other mods can be checked Here
Sad that many of the mods originally intended for farcry were cancelled or moved to other engines. Here are some though
Farcry
X-isle 8
Forgotten war
Obsidian Edge *
tacto
Ultraball
Hard
Doom 3
Classic Doom *
Quake 2 lost marine *
Doom Chronicles
Dawn of the dead
Pathways redux
doom 3 jedi *
*= promising mods unless they are canned ofcourse

Keep adding
