Ok, it’s a really cheesy version of Missile Command and you get unlimited ammo (which cuts way back on the strategy element of the arcade game), but this Easter Egg still works and it’s still fun (assuming the video portion of your video is boring and you just want to listen to the audio):
YouTube, like other Google products, is full of Easter eggs.
For a while, the classic game of Snake could be launched by pressing up and left on the keyboard while a clip was buffering. Sadly, that doesn’t appear to work anymore. But in its place, a game of missile command can be launched by clicking to the right of a video and typing “1980” on your keyboard’s number pad.
I just tested it today (January 25th, 2014) and it still worked. Just go to YouTube, play any video, pause the video, click in any white space outside the video, and type 1980. You’ll figure out the rest.
Other Easter Eggs are listed here. I didn’t test any of them. You’re on your own, but feel free to report back if you find they still work.
UPDATE: Google Image searching for “atari breakout” (without quotes) works, too.