Nowadays there is a dizzying array of cat treats available. Experiment with any of them and see what your cat responds to. Treats however are like candy for you and me. They are meant to be used sparingly. Some treats claim to rid your cats teeth of tartar others have natural cat nip. I think it's a matter of trial and error. No cat treat made for dental care will take the place of a regular check up with your vet that includes a thorough exam of his mouth, or your watchfulness regarding his oral health. Some cats don't like treats at all, and some will come running. If you do find a treat that your cat likes you can use it as a reward in training play, such as fetching and bringing back to you. In this case, take tiny pieces off the treat, or the exercise he's getting fetching that mouse will be offset by his overeating treats.
There are probably more varieties of cat toys on the market than just about any other pet item. The truth is a few simple toys are all your cat wants or needs. Frequently a wadded up piece of paper will entertain him for hours while you work at your computer. I know one cat that gets very upset if someone throws out his well-loved special wad of paper.
Many cat toys have colored feathers. Please remove all feathers from any toy that you plan to leave alone with your cat. These feathers are not the same as the ones his ancestors ate when they caught birds. Those feathers were live feathers; these are dried and dyed with dies that may be toxic and or irritating. A feather teaser, or chaser is fine as long as you are at one end of the toy to make sure he doesn't actually ingest any feathers.
Before I knew better I allowed one of my cats to chew down all the brightly colored feathers on a toy that someone brought for her. She ended up having surgery on an abscess in her throat and the biopsied tissue report read, "foreign protein with aniline die found in the tissue". I have been asked why feathers are used if they are not safe. Sadly I don't have an answer to that question, but they are not safe. So make sure that toys that you leave with your cat have all feathers removed. The same goes for small beads inside of toys, and small bells, and anything that if swallowed could cause a blockage or infection.
A few good toys are all your cat needs. Here are some of our favorite picks.
Peek a prize from www.catsplay.com This solid wooden box has holes all over and you place small toys inside, this stimulates the cat to reach and search and grab toys from inside. Your cat will have endless hours of fun, and probably bring you little gifts he finds inside. Made by SmartCat. Again, remove all feathers from any small toys.
he Sheepskin mouse from www.cattoys.com This is a favorite simple toy. I cut the nylon whiskers off as they could be swallowed once the mouse is demolished, and it will be. These mice are washable and will last a single cat a long time, but get a couple as you will find them hidden in different places as you vacuum. They are blessedly a bit too large to fit into the vac hose entirely, so they can be rescued before they hit the dust bag.
A lot of people who work all day and have a single cat, leave music or TV on for the cat all day. I think it is comforting for him to have some soft noises that he finds familiar. If he starts asking you to tivo all my children I'd become worried that he's getting addicted, but that hasn't happened yet. My cats are fine with animal planet, and one loves the emergency vet episodes. Pistachio will watch intently during any surgery. Maybe he was a vet in another life.
Another super idea is any of the video catnip videos. These can be put on continuous loop if you are a twelve year old or a techno wiz. Or ask someone to do this for you so you can leave it on all day. Just be careful of any soft front TV's as cats will chase what's on the screen and even go behind it when they find the screen unyielding, to see where that thing is.
If your cat is an "only child" it might be a good idea to leave some soft music on during periods or your absence. However if you have arranged his kitty furniture, and he has several resting and playing spots, he should be fine. If you are gone for long periods however it is even more important that you make time to exercise your cat. He needs mental and physical stimulation the same way you do. Cats can and do get depressed and overweight if they lack activity and stimulation. So make sure you make time for this. Short periods of interactive play and some cuddle time should do it.