TowerFall Ascension has a 2-player co-op mode where you and your friend fight against hordes of bad guys. It has friendly fire, so you need to communicate to avoid hurting each other. This creates a mode that motivates you to communicate with your friend more, leading to a lot of back and forth ban...
Each player only has three arrows at the beginning of a match. Once they are fired, the arrows can be picked up by anyone. This way no player can build momentum that feels oppressive, allowing even new players to control the pace of a match since they can just hog all the arrows.
Destructible environments, large explosions, dirt and blood flying everywhere, scaling a wall with just your knife, shooting rockets larger than the body of a man, and many more over-the-top gameplay elements. Broforce is just a blast to play.
Four players can join a single game both locally and online. It just feels really awesome spreading mayhem and destruction with three of your friends as blood, guts, and explosions surround you from all sides.