A redditor called EquinnoxX wanted to propose to his girlfriend, so he hacked an NES console-game cartridge called Contra so that it delivered the proposal in the course of the gameplay. He changed the character names' to his and his girlfriend's, and then modded the end text to be a marriage proposal (she said yes).
"The modified contra code is seen here in hexadecimal on the left and its (almost) ASCII representation on the right. You can see the ending screen text and the credits. That file is loaded and ready to be flashed to the EPROM chip that is loaded (you can see it in the 'Device Location' section on the right). A new NES cartridge is just 28 solder points away!"