Back in the summer of 1994 my cat brought me what I thought was a young chipmunk or squirrel - surprisingly uninjured so far as we could tell. We put it in a cage with some food, expecting that it would die. Soon discovered that it was a flying squirrel. We kept it for a few days to recover from the trauma of being captured by the cat, then released on a mountain in a nearby state park. It's the only one I've ever seen.
Other creature encounters:
We were camped right beside the trail in the HMW last fall. Heard some breathing, grabbed the camera, unzipped the tent. 30 feet away - Moose! Footprints on the trail showed he'd been much closer.
Took off my shoes at one of the GSM shelters. Was standing in the sun enjoying the weather and a little grass under my feet. Was surprised by rattlesnake right in front of me. It touched my foot!