List of games with many different themes

 I recently discovered the site and was surprised by the wide range of free two player games it offers, from quick racing matches to competitive sports and even strategy challenges. I enjoy how easy it is to jump into a game without downloading anything, but I am curious about other people’s experiences. Which games on 2 player games do you think are the most fun or addictive, and do you prefer cooperative options or head to head battles when playing with a friend? Would love to hear your recommendations and thoughts.