[M] - Increase money by $5000
[D] - Information about a tile (or possibly an Item) in the World
[R] - Increase reputation
[Shift]+[R] - Decrease reputation
[G] - Toggle a grid display on the ground
[K] - Change viewpoint/camera
[U] - Increase Tier to the "Top Tier"

The following keys do not require cheats to be enabled:

[Ctrl]+[+] - Increase Gamma
[Ctrl]+[-] - Decrease Gamma

The following keys require a debug mode or other options to be enabled:

[F6] - Toggle Cull Cam (no idea what it does though)