This is a list of games, tricks, and jokes that the folks at Google have put together. All of these can be accessed from Google's homepage

Type do a barrel roll into the search box, and the screen will roll before showing the search results. 

Search tilt or askew and the results page will display tilted. 

Search Atari breakout and click on the image results to play breakout with Google images.

Search spinner and one of the results will be an interactive fidget spinner to play with. 

Search tic tac toe and you can play a game of tic tac toe against the computer.

Search fun facts or I'm feeling curious and Google will give you a randomly selected fun fact.

Search flip a coin and Google will give you a virtual coin to flip.

Search roll a die and Google will give you a virtual die to roll.