Well, Knoydart is incredibly inaccessible, but there's not much there except a bunch of Munros. You have to take the drive all the way to Mallaig on the western coast, then a small skiff to a tiny little village on the edge of the peninsula. It's one of the few places on the Scottish mainland that you can't get to via road.
I'd say Machrie is a bit more accessible than the Outer Hebrides, if only because it's that much closer to Glasgow. I'd think Machrie is probably the best, least-accessible course in Scotland -- some might say Durness, but Durness is only nine holes, and I've heard only one of them -- the clifftop-to-clifftop one -- really stands out.