Dhruin
SasqWatch
A lot of people will be familiar with the System Shock 2 Rebirth project but this article at The Random Gnomes' Random Lair (nice name) has a guide to several mods to bring SS2 up to "2K7" standards. Here's the intro, which aptly describes why SS2 is so good:
More information.System Shock 2 is better than Deus EX, more elaborate than any of the Thief games, scarier then Resident Evil and quite frankly more engrossing than the whole porn DVD collection of planet Earth. In short, it's a fantastic game. A brilliant one too. I mean, it's even got itself a Gamespot retrospective. Unfortunately though, what with being almost retro, its graphics have started to age and their late nineties 3D engine simply doesn't look that scary anymore. Oh, and WinXP, minor gameplay and sound problems have also managed to creep up.