I bought this years ago for my cat Teeny to try. It's a plastic hinged thing that sticks to the corner of the wall and has two removable combs, with space behind for catnip. The idea is, kitty self-grooms and the hair stays in the comb, you just clean it out periodically. Teeny loved it and would rub his cheeks and head on it several times a day. He didn't so much use it as a self-groomer, other than for his head, but for the amusement he got out of it, the $10 was well worth it.
This is an easy product to find in your local pet store or online, I definitely recommend it.

Pros: Daily kitty amusement

Cons: Sticks on the wall with double-sided tape

cats like to rub themselves on corners, so this is a great idea

Pros: works well

Cons: none