If you type "google gravity" and then click "I'm feeling lucky" on Google, the entire page will lose it's gravity and you get to play with it.
Searching for ‘elgooG’ on Google will take you to a Google website that is completely backwards. This backwards version of the ultra-popular search engine will come up directly if you click the ‘I’m Feeling Lucky’ button instead of ‘Google Search.’ The site was originally created just for fun, but has actually become quite useful in China after Google was banned there.