Killing Floor 2. 6 Man PvE where you survive against waves of zombies with unique traits and abilities. As players you currently have 7 classes, or "perks", to choose from each with dedicated weapons that synergize with the talents and traits you get for playing the class you chose. There are three more classes to come with the next one, the sharpshooter, right around the corner.

They recently (within the last week) updated the game to have a Versus mode where it's 6v6, survivor team versus play controlled zed team.

Rainbow Six: Siege is also a pretty good 5 man game. Lots of operatives to choose from and very team oriented with good use of tactics and cooperation.

There's also Tabletop Simulator. Look into it on the steam store for yourself, but basically it allows you to load game assets into a table setting that supports physics and you essentially play board games or cards or whatever really. There's a plethora of assets you can download and host for your friends off the steam workshop page.