Multiplayer first person shooter games for PC/Windows with 4-player online support

Synergy (HL2 mod)

Players: 0 local, 16 online

Starship Troopers

Players: 0 local, 8 online

Team Fortress 2

Players: 0 local, 6 online

DOOM 3: Last Man Standing (Mod)

Players: 0 local, 16 online

Mission Against Terror

Players: 0 local, 8 online

AirBuccaneers

Players: 0 local, 16 online

Interstellar Marines

Players: 0 local, 4 online

Space Hulk: Deathwing

Players: 0 local, 4 online

Sniper Elite 4

Players: 0 local, 4 online

Aliens vs Predator (1999)

Players: 0 local, 4 online

Vietcong

Players: 0 local, 4 online

God Mode

Players: 0 local, 4 online

Dead Island

Players: 0 local, 4 online

Tom Clancy's Ghost Recon Breakpoint

Players: 0 local, 4 online

Combat Arms

Players: 0 local, 8 online

Serious Sam HD: The First Encounter

Players: 0 local, 16 online

Star Trek Elite Force 2 (HZM Co-op Script Mod)

Players: 0 local, 12 online

The Darkness II

Players: 0 local, 4 online

Call of Duty: Black Ops

Players: 0 local, 6 online

Aliens vs Predator

Players: 0 local, 4 online

Painkiller Resurrection

Players: 0 local, 4 online

Serious Sam HD: The Second Encounter

Players: 0 local, 16 online

Conflict: Vietnam

Players: 0 local, 4 online

ORION: Prelude

Players: 0 local, 5 online

Aliens: Colonial Marines

Players: 0 local, 4 online