I havent had much experience with mods in games but if anyone has had any well built mods in the gaming world post them up with the game it was in. 
Brilliance. XDHardRockSamurai said:This one for Left 4 Dead:
OHHH SNAP ! That beats everything I wanted to write.HardRockSamurai said:This one for Left 4 Dead:
Yup. I was going to name that one :3Quick Ben said:My favourite is OOO (Oscuro's Oblivion Overhaul) for (suprise!) Oblivion. It fixes the problems with the level-scaling, makes the game harder, improves replay value, and generally makes the game better.