This is a video of the hacked Legend of Zelda game that Imgurian jadowdl used to propose to his girlfriend (links to her telling of the story). He altered the text and animation after beating Ganon, as well as gave Zelda bunny ears (because his girlfriend loves bunnies), and the two speed-ran through the game one Saturday in six hours, resulting in this proposal. Beautiful, right? I'm going to convince my girlfriend to watch me play all of Fallout 4 for a very, VERY special bonus at the end. Then when the end comes and there's no proposal she'll break up with me, and I'll tell her that was a test and that's how I know she's not the one for me. I will call her crying for months after.
Keep going for the video, as well as a shot of the beautiful Zelda inspired ring.
Thanks to Jeffrey S, who hacked the end of the NES version of Battletoads to propose to his girlfriend but they still haven't been able to beat it together to see the proposal. That was two years ago.