All the classic Halo games in one, now on PC with PC|Xbox crossplay. We have nothing else to say here, except... buy it!

Definitely the SEXIEST game ever made. No more words. Buy it.

It is so sad to see that Portal 2's co-op is kinda dead. It may take a while for you to find a game. However, it has an amazing campaign and co-op mode with the ability to create your own maps.

The second CoD released in '05 is definitely a classic. This game of full on epic. With a classic multiplayer mode, and an amazing campaign set in WWII, this will keep your face stuck to the screen.

Basically the campaign mode of CS 1.6 and easily moddable, allowing you to add more mission packs. The stock mission pack called Condition Zero is very fun. This comes free with CS 1.6.

Essentially just fanmade Half-Life: Opposing Force 2. It received hatred at release, being called the first failed Half-Life game, but the developer has updated the game. Definitely worth a try!

Day of Defeat doesn't get as much credit as it deserves, Valve's first WW2 game in the GldSrc engine is very underrated. Day of Defeat is a fast paced strategy FPS, and it's totally worth $5!

Valve's retake of the classic Quake mod. The Team Fortress series is another huge classic. Team Fortress Classic deserves more players and credit than it gets. Definitely worth a play and $5!