Borderlands, Borderlands 2, and Borderlands the Presequel.
These three games are amazing. For me these games hold some extra meaning rather then just being very fun to play. They are all supportive of cooperative play. Which is how I have played all of them. My girlfriend and I started playing them together even before we started dating. She is my only friend who enjoys first person shooters and well Borderlands in my opinion is the best first person shooter to date. It has amazing game play and humor.
I played through the 2nd one entirely with my girlfriend and we beat it. Now the first and the presequel I have not beat yet with her but we are working on them. The humor in the game is what keeps us playing through all of them. Though we both equally hate the character called Claptrap.
Just imagine a futuristic world where the guns start off by firing normal bullets and upgrade to firing massive bolts of energy/lighting/plasma/or something equally massive. Then the monsters you are killing go from being cute dog like things to baddies several stories tall and able to kill you in one swing if you take a direct hit. It is such a lovely game so full of characters that you will remember for a long time. What is even better is that the story arc is funny and keeps you on you toes. With everything that happens I know that I was sucked into one sad tale or another, but killed many baddies in revenge for the lose throughout the games.
In any case I would recommend this game to everyone.
Thank you for reading. Have a wonderful day.