Depending on how many people are playing, these are some fun (and generally silly) couch co-op games that I've enjoyed playing with my wife and friends, which also go on sale frequently enough
- Cat Quest 2 (only two people)
- Totally Reliable Delivery Service (I think also only two)
- Tools Up (up to 4)
- Overcooked 2 (up to 4)
- Boomerang Fu (up to 4)
Edit: just wanted to note that the first 4 are co-op, and the fifth is not