1. Obli-Gator
  2. Oblique Angel
  3. Obscene Jester
  4. Obsolete Techie
  5. Obtuse Angler
  6. OctoBear
  7. Octopuss in Boots
  8. Offense Attorney
  9. Ogre Achiever
  10. Old Town Rogue
  11. Olfactory Worker
  12. Omniscient Ignoramus
  13. Omnomnomnivore
  14. On-and-off Guard
  15. One-And-A-Halfling
  16. One-and-a-Halfling
  17. One-Armed Archer
  18. One-Armed Bandit
  19. One-Eyed Beholder
  20. One-hit Wanderer
  21. One-Hit Wonder
  22. One-Legged Centipede
  23. Onion Ringleader
  24. Onomatopoet
  25. Open Sorceror
  26. Operetta Phantom
  27. Optical Illusionist
  28. Optimus Slime
  29. Orc Angel
  30. Orc de Triomphe
  31. Orc of the Covenant
  32. Organ Grinder
  33. Origami Dragon
  34. Original Impostor
  35. ORLY Owl
  36. Orthodontisaur
  37. Oscillating Fanboy
  38. Ottoman Umpire
  39. Out-of-Commissioner
  40. Out-of-Frame Monster
  41. Out-of-Service Dog
  42. Out-of-Shapeshifter
  43. Out-of-Tuna
  44. Out-Sorcerer
  45. Outsourced Monster
  46. Oval Lord
  47. Over-Confident Noob
  48. Overbearing Waiter
  49. Overconfident Noob
  50. Oxy-Moron
  51. Ozone Slayer