While replacing my u-joints earlier I decided to track down a rattle while I was underneath and found it... In the form of the e brake line bracket.. They were both just hangin' out unsecured from the upper control arms. So I tossed a couple nuts on them, gave the Jeep a shake, problem solved.
Mystery not solved however, I'm trying to figure out why the PO would have removed them from the control arms. The Jeep wasn't lifted when I bought it so that rules out stretching... I think. There's no way they could have rattled loose?