So after seeing the really cool Stalker 2009 mode that remakes the entire game in modern Crysis-like graphics, I'm curious about what user-created content has been made over the last 20 years. It seems (at least these days) that almost every PC game has at least a few mods made for it and many make the core game experience better. For example, I recently played Fallout 1 and something as simple as an interface mod that let you change equipped weapon a mouse wheel click made the game infinitely more enjoyable. So what are some great mods for games? I'm especially interested in offline Single Player mods (since I don't online game much), and mods that improve the core game either graphically or gameplay-wise or completely rehaul to be a whole new experience.