Deus Ex, the 2000 classic that was years ahead of its time, has not aged well. So the fine folks at Ion Storm and Caustic Creative have seen fit to recalibrate the entire game with Deus Ex: Revision, self-described on Steam as a "community-made overhaul" that "features new environments, news music, and new world-building detail."
It essentially compiles all of the most popular mods by the fanbase including high-resolution textures, Direct3D 9 rendering, better 3D moeling, and a new soundtrack by EdenShard. Just be sure not to get too frustrated with the game at the beginning when your gun accuracy is pitifully low; you'll need to improve your weapon skills to have any chance.
You will need to have Deus Ex: Game of the Year Edition installed in the same library as Deus Ex: Revision to play it, but if you do, the update is completely free of charge. Otherwise, you can silently nab the game for just $1.39 (80% off) in the Steam Stealth Sale that runs until October 16.