For me I think it would have to be Ace bandages. When I was a kid I played with those things all the time. If you had enough you could even wrap yourself up as a mummy. Even now I can’t resist wrapping up a leg or an arm every now and then. And as an added bonus there’s something comfortable about being tightly wrapped up in their soft cloth.
What else is good?
shoe-horns! I work in a shoe store (not like Al Bundy though) and of course we have hundreds of shoe-horns. I am entertained for all of my downtime their just hitting the curved end and making it fly like 5 feet across the room… what’s really fun is stepping on it hard, at just the right angle, and trying to catch it in mid-flght!
Air jets. I’ve played the Star Spangled Banner on both hand washers and an airbrush.