System Shock 2
System Shock 2: co-op for up to 4 players, on Linux, PC and Mac, came out 11 August 1999.
Want to play System Shock 2 with friends?
Pick a night together in Lobbli: everyone marks when they are free, and you see which evening works.
Quick answers
Is System Shock 2 co-op?
Yes, System Shock 2 has a co-op mode.
How many players?
Up to 4 players.
Split screen?
No split screen mode is listed for it.
When did it come out?
11 August 1999.
Which platforms?
Linux, PC and Mac.
What kind of game is it?
Shooter, RPG
Who makes it?
Looking Glass Studios, Irrational Games
From its Steam page: co-op, player count.
About System Shock 2
A first-person cyberpunk exploratory horror RPG and sequel to System Shock (1994) in which a soldier wakes up in the starship Von Braun in the aftermath of a disaster and finds himself in the midst of a conflict between SHODAN, the artificial intelligence antagonist of System Shock seeking mastery over humanity, and The Many, a flesh-based psychic hive mind led by the ship's corrupted AI.