The Forest is almost a MUST if you like survival games and co-op. Here:
- Killing Floor 2
- Sid Meiers Civilization V
- Bioshock Infinite
- BattleBlock Theater
- Battle vs Chess (<- personally one of the coolest among these)
- Breach and Clear
- Deus Ex: Human Revolution
- Interstellar Marines
- Metro 2033 (or the series, pref. the redux)
- Natural Selection 2
- Oceanhorn: Monster of Uncharted Seas
- Portal 1&2
- Quake/DOOM (any of the games are good, except for that other one....)
- Saints Row IV
- The Ship
- Sir, You Are Being Hunted
etc.