I posted this on the Steam forums, but since I own DC from GOG too, I figure I'll post it here as a resource if you're interested in seeing what you can do with the developer mode. If anyone else has found other keys that work, let me know. I'm sure I've missed some of them.

Ctrl+Y = complete quest 'By The Book' (gold, EXP, loot choice)
Ctrl+A = stuck in loading screen
Ctrl+S = turn off sound
Ctrl+F = Load autosave
H or Ctrl+H = Hides UI (for nice menuless screenshots)
Ctrl+K = Removes all inventory items (including quest items)
Ctrl+L = Crash
Ctrl+Z = Toggle markers
Ctrl+X = Level up
Ctrl+C = Open battle tower storage
Ctrl+V = Open blank book
Ctrl+M = Mute
Ctrl+2 = Spawn Tribal Goblin Chief (level 4)
Ctrl+3 = Spawn Tribal Goblin Warrior (level 2)
Ctrl+4 = Spawn Tribal Goblin Ranger (level 4)
Ctrl+5 = Spawn Tribal Goblin Shaman (level 3)
Ctrl+6 = Spawn Tribal Goblin Healer (level 3)
Ctrl+7 = Spawn Zombie (level 40)
Ctrl+8 = Spawn Zombie (level 41)
Ctrl+9 = Spawn Zombie Jake (level 39)
Ctrl+0 = Spawn Troll (level 1)
Numpad 1 = Teleport to a higher point
Numpad 2 = Teleport forward (good chance of getting you stuck in geometry)
Ctrl+Num1 = Toggle 'HUD Text Output' text
Numpad 4 = Turn movement controls 45 degrees CCW (left becomes down and left)
Numpad 5 = Sync movement controls to normal
Numpad 6 = Turn movement controls 45 decrees CW (left becomes up and left)
Numpad 9 = Autosave
Ctrl+Num9 = Load autosave but with message stuck on screen