Just go in and leave them on the counter and walk out.
When I moved 5 years ago I tried to get rid of some games(like 10 or 15)and didn‘t want to bother with selling them.
So I just put them on the sidewalk with a note that anyone should feel free to take them.
A couple of days later Fifa 08 was still there along with King Kong.
I guess nobody wanted that easy 1000 gamerscore.