A dead hunter dropped out of the sky into the hard-to-find area outside the DB sanctuary. Uh, hail Sithis? But that wasn't the most random event I've encountered...
There was a firefly (torchbug) appearing during the daytime at the end of the bridge opposite Riverwood. It was weird to see one during the daytime but I ignored it. But the bug never seemed to leave. After three or four days I decided to pluck the thing.
I swear, ominous music began to play the second I grabbed that bug. Real ominous. I immediately saw a red dot on my compass just past the spot where I grabbed the bug. Dead center of my compass and staring at me like an angry eye. I didn't see anything but the enemy was somewhere on the west bank of the river upstream towards Lake Ilinalta.
I didn't have time to search for it though because a dragon (blood? elder?) flew overhead at the same moment. As I whirled around looking for the dragon, I could clearly see there were now two dots on my compass.
I eventually found the dragon as he flew towards Riverwood. I raced across the bridge to help kill the dragon. A guard died but thankfully everyone else in town survived.
After the fight, I returned to the other side of the river to look for the other enemy. I never did find it and have no idea what it was. I'll say this, though, I'm going into stealth mode the next time I decide to harvest a persistent firefly.