Below are the combinations to unlock all of the safes in Dishonored!

Mission 1 - Dishonored: 451

Mission 2a - High Overseer Campbell (in Dr. Galvani's house): 287

Mission 2b - High Overseer Campbell (by Overseer's building kennel door): 217

Mission 2c - High Overseer Campbell (at Overseer's base): 203

Mission 3a - House Of Pleasure (Slackjaw quest): 138, 656, 679, 696, or 879

Mission 3b - House Of Pleasure (in Artist's house): 656 or 696

Mission 4a - The Royal Physician (at the top floor of the building): 437 or 473

Mission 4b - The Royal Physician (behind the painting): 294

Mission 6 - Return To The Tower (in Lord Regent's quarters): 935

Mission 7a - Flooded District (after you dive in the water to get in): 428, 525, 528, or 628

Mission 7b - Flooded District (Old Port District Sewer): 428, 525, 528, or 628