Someone also mentioned Starsiege Tribes

That is also one of the most revolutionary games of all time. Its the only game that I know that uses jetpack in a FPS game. Its soo addicting, too bad no one plays it anymore, but they did come up with Tribes Vengence, Im not sure if people play it though. Disc launchers were amazing, it was extremely satisfying to get a Midair shot.. :D

Definitely Mafia.

I found this game to be one of the best action games on the PC in the past 5 years, and I enjoyed it more then any of the GTA games, yet it didnt get nearly the attention.

Robnyc22

whoa i was thinking the exact same thing.. I was wondering if anyone was going to say it.. but thankfully one of the first post was Mafia! Great storyline, great action, great voice acting, and great music too.