What are your favorite mods that breathe life into old games?

[#1]

Plundered the sale on GOG recently and picked up a ton of older shooters. Soldier of Fortune II, SWAT 4, Hidden & Dangerous 2, I.G.I. 2, XIII, Far Cry 2 etc and I was so psyched to see that some of these have mods that increase the longevity of the game, and even in cases like SWAT 4 are still releasing updates.

What are your favorite mods for old games that help them stay fun & playable today?

[#2]

I pretty much gave up on PC gaming nearly 20 years ago when the original Xbox came out, but before then I remember playing a Quake 3 clone based on Star Trek Voyager called Elite Force that was pretty cool.