Made in 98, but still better quality, play, and design than most games on the market in '05.  Good storyline, great AI and graphics, not-overly aggressive system requirments, tons of add-ons available.  Incredible single player mode, good weapon selection, and arguably one of the best FPS online games of all time.  If you like HALO, you will like Halflife.  Very similar, but no limit on how many weapons you can carry, and the levels aren't as repetative.  (My biggest complaint about Halo, though it's obvious why, many of the levels and hallways are exact copies of one you've seen dozens of times already...gives a feeling of being lost, and even fed up at times.) Halo does have the edge as far as cars and what not though. I also recommend Halflife 2, the sequel to what I'm talkin about here...  INSANE graphics and gameplay.