Unlimited money:
Pause game play and press A, Z, X, Y.

Slot machine cheat:
Build a marina and supply power to it. Go to the Budget/City Ordinances option and enable Legalized Gambling. Highlight the sailboat and press the L. A slot machine will appear 25% of the time when this is done. Each play of the slot machine costs $10. The effect of the slot machine is dependent on if the Disasters option is enabled.

If Disasters are enabled, you can win:

Money (95% chance of wining 5% of your total current funds, or 5% chance of losing the same amount)
Destruction of random location on map.
All rubble in city is replaced with trees.
Fire starts in a random location.
The oldest power plant has its age reset to zero.
If a fire is currently burning, it will be replaced by a flood.
A tornado starts, unless one is already present.
Two more mystery prizes.