| Game | Rating | Download |
|---|
| Oedo Fight (Japan, Bloodshed version) |  | |
| Oedo Fight (Japan, Bloodless version) | | |
| Offensive (Spanish bootleg of Scramble) | | |
| Ougon no Shiro (Japan) | | |
| Oh My God! (Japan) | | |
| Oishii Puzzle Ha Irimasenka | | |
| Oriental Legend Super / Xiyou Shi E Chuan Super (ver. 101, K... | | |
| Oriental Legend Special / Xiyou Shi E Chuan Super (ver. 100,... | | |
| Oriental Legend Special / Xiyou Shi E Chuan Super (ver. 100,... | | |
| Xiyou Shi E Chuan Super (ver. 103, China, Tencent) (unprotec... | | |
| Arcade Database | | |
| Arcade Database | | |
| Oriental Legend 2 (Korea) / Xiyou Shi E Chuan Qunmoluanwu (W... | | |
| Oriental Legend 2 (Korea) / Xiyou Shi E Chuan Qunmoluanwu (W... | | |
| Arcade Database | | |
| Arcade Database | | |
| Oli-Boo-Chu | | |
| Oli Bug (Jump Bug bootleg) | | |
| Omega | | |
| Omega (earlier) | | |
| Omega (bootleg?) | | |
| Omega Fighter | | |
| Omega Fighter Special | | |
| Omega Race (set 1) | | |
| Omega Race (set 2) | | |
| Omega Race (set 3, 7/27) | | |
| Omni | | |
| One Shot One Kill | | |
| One + Two | | |
| One + Two (earlier) | | |
| Onna Sanshirou - Typhoon Gal | | |
| Onna Sanshirou - Typhoon Gal (bootleg) | | |
| OOPArts (prototype, joystick hack) | | |
| Opa Opa (MC-8123, 317-0042) | | |
| Opa Opa (Rev A, unprotected) | | |
| 2 On 2 Open Ice Challenge (rev 1.21) | | |
| 2 On 2 Open Ice Challenge (rev 1.2A) | | |
| Operation Wolf (World, set 1) | | |
| Operation Wolf 3 (World) | | |
| Operation Wolf 3 (Japan) | | |
| Operation Wolf 3 (US) | | |
| Operation Wolf (World, set 2) | | |
| Operation Bear (bootleg of Operation Wolf) | | |
| Operation Wolf (Japan) | | |
| Operation Wolf (Japan, SC) | | |
| Operation Wolf (US) | | |
| Orbitron | | |
| Orbs (10/7/94 prototype?) | | |
| Ordyne (World) | | |
| Ordyne (Japan) | | |
| Ordyne (Japan, English Version) | | |
| Orius (ver UAA) | | |
| Oriental Legend / Xiyou Shi E Chuan (ver. 126) - MAME machin... | | |
| Oriental Legend / Xiyou Shi E Chuan (ver. 105, Korean Board)... | | |
| Oriental Legend / Xiyou Shi E Chuan (ver. 105, Taiwanese Boa... | | |
| Oriental Legend / Xiyou Shi E Chuan (ver. 111, Chinese Board... | | |
| Oriental Legend / Xiyou Shi E Chuan (ver. 111, Korean Board)... | | |
| Oriental Legend / Xiyou Shi E Chuan (ver. 111, Taiwanese Boa... | | |
| Oriental Legend / Xiyou Shi E Chuan (ver. 112, Chinese Board... | | |
| Oriental Legend / Xiyou Shi E Chuan (ver. ???, Chinese Board... | | |
| Oriental Legend / Xiyou Shi E Chuan (ver. 112) - MAME machin... | | |
| Arcade Database | | |
| OutRunners (World) | | |
| OutRunners (Japan) | | |
| OutRunners (US) | | |
| Psycho-Nics Oscar (World revision 0) | | |
| Psycho-Nics Oscar (Japan revision 1) | | |
| Psycho-Nics Oscar (Japan revision 2) | | |
| Psycho-Nics Oscar (US) | | |
| Osman (World) | | |
| Operation Thunderbolt (World, rev 1) | | |
| Operation Thunderbolt (Japan) | | |
| Operation Thunderbolt (Japan, SC) | | |
| Operation Thunderbolt (World) | | |
| Operation Thunderbolt (US, rev 1) | | |
| Operation Thunderbolt (US) | | |
| Arcade Database | | |
| The Outfoxies (World, OU2) | | |
| The Outfoxies (Korea?) | | |
| The Outfoxies (Japan, OU1) | | |
| The Outfoxies (Japan, OU1, alternate GFX ROMs) - MAME machin... | | |
| Out Run (sitdown/upright, Rev B) | | |
| Out Run (bootleg) | | |
| Out Run (deluxe sitdown) | | |
| Out Run (deluxe sitdown earlier version) | | |
| Out Run (deluxe sitdown) (Enhanced Edition v2.0.3) - MAME ma... | | |
| Out Run (deluxe sitdown) (Enhanced Edition v1.0.3) - MAME ma... | | |
| Out Run (Japan, deluxe sitdown) (FD1089A 317-0019) - MAME ma... | | |
| Out Run (sitdown/upright, Rev B) (Enhanced Edition v2.0.3) -... | | |
| Out Run (sitdown/upright, Rev B) (Enhanced Edition v1.1.0) -... | | |
| Arcade Database | | |
| Out Run (sitdown/upright, Rev A) | | |
| Out Zone | | |
| Out Zone (old set) | | |
| Out Zone (older set) | | |
| Out Zone (oldest set) | | |
| Out Zone (Zero Wing TP-015 PCB conversion) | | |
| Out Zone (harder) | | |
| Over Top | | |
| Ozma Wars (set 1) | | |
| Ozma Wars (set 2) | | |
| Ozon I | | |
