No One Lives Forever
I got the first No One Lives Forever game when it came out in late 2000, but thanks to a frustrating series of events, I didn't complete it until six years later. The game ran poorly on my Windows 98 POS computer, and stuttered its way through outdoor environments even at the lowest settings. I didn't advance far before the computer crapped out and I lost my save, and lost my interest for a while. Later we got a new machine, and the game ran perfectly. I got much farther in the game before the hard drive pooped out and I lost my save again. In the Fall of 2005, I got my own computer, which kicked the old one's ass, and checked the game out, but was preoccupied and didn't get around to actually playing through it a year later. Despite this long, painful road to completion, I still saw how good a game it was.
It doesn't have the amazing gameplay and physics engine of Half-Life 2, and some of the cinemas seem awkward, but it's quite a good stealth-based shooter. I say stealth-based, but rarely do you actually have to be stealthy, most of the time you can just cap fools as you please. The game's brilliance mostly comes from the writing, which is both hilarious and intelligent for most video games. It creates a fun and self-referential world that's fun to be a female James Bond in. If you never played it, you should look past the now-dated engine and graphics and give it a go.