Like everything in biology, there's one, unified answer: It depends.

Specifically, how do you define "exoskeleton"?

If you define it broadly enough to simply be a hard, outer layer, then basically everything with armor fits the bill: turtles, armadillos, oysters, etc. Even a variety of protists like diatoms.

If you say it has to support body weight, it gets more tricky, but there a few examples that squeeze in here: turtles again, crocodiles have specialized muscles to "brace" against their armored hide when walking, etc.

If you specify that it has to be involved in turning muscle shortening into body motion, like in arthropods and with our endoskeleton, nematodes may fit the bill, as they have a collagenous "cuticle" which inertnal muscles attach to. But it's not truly "rigid" the way an arthropod exoskeleton is (think of it like stiff rubber).