Here's one that's probably not mentioned here so far: Shattered Horizon. It was a multiplayer FPS set in Earth's orbit with extremely low gravity. You could right yourself on any surface and fly around anywhere, making matches unpredictable. The developers ultimately disabled purchases of the game on Steam when they could no longer support it. They did at least add bots in the game's final update, but if you want to play it now you're out of luck unless you can somehow find an unused code for an obscure PC game that's over a decade old...
Damn, I was just Ctrl-F'ing my way through this to see if anyone had mentioned Shattered Horizon. Glad someone remembers it. I didn't like it as much when they added the extra guns in the firepower update. I liked my combo assault/sniper rifle. The best part was that you could power down your space suit so that you were running silent. You'd lose all the audio sound effects except for your breathing and your own gun (or bullets that were hitting you). In exchange you wouldn't show up on enemy radar and you wouldn't be highlighted on an enemy HUD. If you aimed yourself right before you shut down you could sneak up on people without alerting them and OHKO them with your pick.
The game was made by Futuremark Games Studios, the guys who make benchmarking software. It was restricted to DX10 only and even by late 2009, only 30% of Steam users had a DX10 GPU and Vista so the player base wasn't huge to begin with. It's probably one of my favourite multiplayer FPS games ever.
Splinter Cell Chaos Theory - Mercs vs. Spies mode. So much tension it often felt like a horror game.
The first GunZ: The Duel. I guess there are still some private servers now but it's probably just the top of the top playing there. Originally released in 2003 in Korea and 2006 everywhere else, it was shut down in 2012. Had a ton of fun in 06-09, really wish there were a modern equivalent with it's style of movement
This.
1 vs. 100 is the only one that I think is completely unplayable in any form to this day. I have nostalgia for Mario Kart DS and Halo 3 but if I wanted to I could probably play MKDS with a hack and people still play Halo 3 today. There's nothing else like 1 vs. 100 and it's completely gone.
Fuck natural selection was such a fun time. I'm pretty sad it never caught on.
Warhawk.
That game was everything during my sophomore year of college. Countless days spent in 4 player split screen coordinating strategies on-the-fly during some amazing CTF matches. Huge levels, infinite draw distance, well balanced vehicles & weapons, dog fighting, and a pitch-perfect arcadey representation of that adolescent 'army man' battlefield approach.
Man, I clocked hundreds of hours in this game. All those Claimh Solais runs, the miser rings runs, the winged boots runs, etc. Going as fast as possible with friends for optimal hunting. Even after they released the Getsu Fuuma chapter people continued asking for more but they just stopped supporting it.Castlevania: Harmony of Despair - Sad to have sen this community to die off after a few months. I loved doing runs when you had a good group going. I remember having a pretty badass Charlotte
What a game. Looked unbelievable for the time, and was the first 6DOF shooter I had the chance to play during it's heyday. I'd love for it to come back.