Portal 2 is a first person puzzle game from Valve. It features a single player and co-op campaign with mind bending puzzles.
Don't Starve Together is an indie survival game with roguelike elements.
TowerFall Ascension is a 2D local online shooter with gameplay that sees players platforming in an arena trying to shoot one another with limited ammo. There is also a co-op mode where players fight wave after wave of enemies.
Explore a neon galaxy in your very own battleship in this 1- or 2-player couch co-op adventure.
2 player simultaneous coop platformer. Available from many a flash game site.
The Cave is a puzzle-platformer created by Double Fine Productions that costs $14.99. Three players choose from seven characters, drawn from across time and space and harboring dark secrets, believing they can learn something about themselves and who they might become.
Forced is a 1-4 players action role-playing game with a top-down view for up to four players in the combat arena. Players must select a weapon class and choose between different abilities to combat the various enemies of each arena, while solving puzzles using the help of Balfus.