A few of my favourites:

https://www.google.com/search?q=do+a+barrel+roll

https://www.google.com/search?q=zerg+rush

https://www.google.com/search?q=atari+breakout&tbm=isch

"search?hl=en" is also needed for the original link, if you are living in e.g. germany. The easter eggs seem to only display on "www.google.com".

https://www.google.com/search?hl=en&q=kerning

It's actually working without hl=en if you're from germany, even on google.de