I love co-op games. A few of my favorites (in no particular order) are:
Fallout (w/ Atomic Bonds expansion of course)
The Crew (either version)
Black Orchestra
Stars of Akarios
Forbidden Desert
Gloomhaven
Mysterium
Arkham Horror LCG
Spirit Island
Honorable mention for some semi-co-ops:
Fury of Dracula
Specter Ops
Dead of Winter