This has to be one of my all time favorite games, ever. The jump from Doom to Quake was exponential in terms of graphics, play-ability, story line and LAN play. Not to mention we were also blessed with the original Team Fortress Mod. I lived that game for a few years on mPlayer and later QuakeWorld (on a 56k modem no less!).
Quake in 1080p:
QuakeWorld Team Fortress:
Quake Team Fortress Opening Intro:
There was an updated game made a few years back for Team Fortress. It's called Fortress Forever. It seems to capture the original game very well.
I can't believe I almost forgot to include the soundtrack. It was done by Nine Inch Nails. It set the mood a little too well sometimes.