Below is a list of every single map lasted as "co-op", meaning it requires 2 players working together to complete. They are first sorted by difficulty, then a raw alphabetical list.
Novice
Frienemy (Puzzle)
Jko-op (Parkour, Search)
Moderate
Brothers' Therapy (Puzzle, Parkour)
Heist (Puzzle)
Very Hard
Kakashi (Adventure)