coins and free play...
working nickle and dime mechs on machines that should have them...
i tumble up quarters as needed and make them all shiny, then put them in bowls of them close to the machines...
i have them free play modded just in case someone wants to "just push the button", but everyone seems to prefer dropping a coin... invariably they will feed the machine when the credit reel reads zero...
plus it's a "parts piggy bank"...