One of our last adventures in the Smoky Mountains was a hike to Mouse Creek Falls, but what was great about this one was the creek -- called Big Creek -- along the trail that goes up to Mouse Creek Falls. Big Creek is full of giant boulders and lots of smaller waterfalls, but the best part is the many big and deep swimming holes. These are off the main trail, and we didn't see a single other person at any of these until we got to the biggest one, the Midnight Hole. We ended up spending most of the hike hopping up the boulders in the river, instead of on the trail, and it was tons of fun.
The one thing I didn't like about this trail was the "no pets" sign on it. Not that we currently have a dog, but if we did, we'd definitely want to take him on hikes like this. And there were clearly horses on this trail, as evidenced by the giant piles of horse poop that their stupid owners always fail to clean up, so it's a little ridiculous that you can't bring a dog here.