Video game endings may be some of the best in media, because you can affect them. Nonetheless, my top three are more straightforward, as in
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https://youtu.be/y6NGn9bA304?t=151 World Heroes 2 Jet Best Ending, because it's so random!
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Limbo of the Lost. The game, the myth! https://www.youtube.com/watch?v=URcvdDtnM_0
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Stack Columns: https://www.youtube.com/watch?v=vufEmB3qSNA So bittersweet!
What are your favorites?
Off the top of my head, Super Metroid and Braid endings both did something unusual and interesting for their time. Undertale as well, though that's already been mentioned.