- ODM 2
- OFG 4
- OGMirageOG (Overkill Games UK) 4
- ONS-Recon 2
- OUTOFANSER 2
- O_Senad (Mr.Invisible) 2
- Oak 4
- Ob1-Kenobi 3
- Obi-Wan 3
- Oblivion_Soldier 2
- Occam 3
- Octavian "VikingWasDead" Ornoch 12
- Octopussy 2
- OddMods Team 2
- Odedge 19
- Odhinn Kohout 3
- Odin "Bareodin" 2
- Odysseus 2
- Ogr81 4
- Oh yeah!' Nabors 2
- OjitroC 6
- Oki "MAVERICK" Blatnik 4
- Ola 3
- Ola 'Jolle' Frid 12
- Olav 'Tonito' Åsheim 4
- Olav Gjerde 17
- Olav Groenaas Gjerde 2
- Old Geezer 19
- OldUnreal 5
- OldeDevil 3
- Olethros 2
- Oli "Olister" Wood 6
- Olindo -=BlueSilver=- Bottura 2
- Oliver 'PlagueLord' Gerestein 3
- Oliver 'Raz' G. 2
- Oliver 'WinRAZ' Garrigue 7
- Olivier ''Neuro'' Chapuis 5
- Olivier koos 4
- OmegaDelta 2
- OmletteDuFromage 6
- On@g@ 4
- Ondoher 3
- Ondrej Vojta 3
- One Man Clan 3
- OpFor 2
- OpNox 5
- OpticalShadows 3
- Orbit )BoM( Clan 2
- Ordzo 4
- Organized Evolution 2
- Original Author: Alan 'Talisman' Willard 2
- Original-Cliff Bleszinski/Rerun-Itchy-Muff 2
- Original-Myscha /ReRun Itchy-Muff 2
- Original-Myscha the Sled dog/Rerun-Itchy-Muff 2
- Original-Myscha\Tweaked by Itchy-Muff 2
- Original-Shane Caudle/Rerun-Itchy-Muff 2
- Original: Toady - Ported: sp1ral 5
- Original: Vanx 2
- Originaly by Dave Ewing 2
- Orignal: Shinigami 3
- Orion 2
- Orion(Co30) aka Mouse(Co30) 2
- Oscar Crego 8
- Oscar Ortigueira "SuiciSpai" 4
- Otto 'Format Life:' Rask 3
- Otto Rask 2
- Otto Rask ( Format Life: ) & MsM 2
- Oukill@ 3