Unlimited money
Start a game and select any nickel slot machine. Insert 100,000 credits into the machine, then return to the slot machine menu. Select a $1000 slot machine and your credit total will have increased. Return to the slot machine menu, then select any nickel slot machine. Insert 999,999 credits into the machine, then return to the slot machine menu. Select a $1000 slot machine, and your credit total will be even larger.