Would any of these magic items be usable by a muggle?

Anything from LOTR which was used by men, dwarves or hobbits should work for normal humans. I think the invisibility cloak from HP would probably work for muggles, if they know what it is. The One Ring could be worn by a muggle, although I doubt they'd enjoy the experience. For most of the other stuff, they either wouldn't know how to use or it would have some disasterous consequences if activated by someone who didn't understand it.