Joseph "Rawr" Thai's Mario-themed doorbell makes a coin-chime every time its pressed, and increments an LCD counter showing how many coins have been racked up by visitors to the house. Every ten presses, the doorbell plays a 1UP sound, and after 100 presses, it plays a mushroom upgrade chime.
Rawr's got detailed plans for building your own Mario doorbell.
Who wants a boring old doorbell that simply goes "ding dong" when pressed? I sure didn't! That's why I decided to design my own doorbell that provides ample entertainment for the guest at the door. Now, introducing the new Mario Doorbell; it's flashy, it's got coins, and it's guaranteed to increase the frequency of ding-dong ditchers or your money back! In fact, your guests won't even be at your door to visit you, they'll be too busy racking up coins to even notice you.
(via Oh Gizmo)