| Title | Year | Genre |
|---|---|---|
| Obut Petanque 2 | 2012 | Sports |
| Of Orcs and Men | 2012 | Action |
| Omega Five | 2008 | Shooter |
| Omerta - City of Gangsters | 2013 | Management |
| Onechanbara - Bikini Samurai Squad | 2013 | Beat em up |
| Operation Darkness | 2010 | Strategy |
| Operation Flashpoint - Dragon Rising | 2009 | FPS |
| Operation Flashpoint - Red River | 2011 | FPS |
| Orange Box, The | 2007 | Compilation |
| Orc Attack - Flatulent Rebellion | 2013 | Beat em up |
| Otomedius Excellent | 2011 | Shooter |
| Ougon Musou Kyoku X | 2011 | Management |
| Outland | 2011 | Action |
| OutRun Online Arcade | 2009 | Racing |
| Over G Fighters | 2006 | Aerial fighting |
| Overlord | 2007 | Strategy |
| Overlord II | 2009 | Strategy |
