A short and easy singeplayer and local co-op game. Unfortunately, you can't play online but the overall game is fun to play through. Never buy at full price because it goes on sale for very cheap.

Farm with your friends! You can marry each other too ;). Beware, money is shared between players. Don't go spending all of it at once! (speaking from experience)

Mass murder monsters with friends or just party with emotes! Joining a private game can be annoying but very worth it. PS: Hammer best weapon, change my mind.

Quake Champions is a fast paced AFPS that has unique characters with different abilities. While not the best AFPS, it offers a lot of fun with friends using the party system. Would not recommend solo.

While not really a super good Resident Evil game, RE5 offers a great co-op experience with a friend. Also has a meh PvP mode.

The campaign, while amazing, has no co-op. Multiplayer and Snapmap exists, though. Snapmap has the only co-op experience in the game and is fun to waste hours in with friends.

Probably one of the best co-op (and PvP) zombie game on Steam. Many campaigns, vanilla and workshop, offers huge replayability value. Best played with friends over voice chat.

A fairly difficult game that offers a great co-op and PvP experience. Password system that makes it easy to co-op with people you want. Beware of invaders, though. PvP fightclubs with friends are fun.

Battlerite offers an intriguing two or three player brawling experience following the core idea of MOBA-like team fighting. Team play and team composition is very important for success.

Sanctum 2 offers a fun and balanced co-op system for parties of one, two, three, or four players.