One of the random encounters I... erm, encountered was an Ice Mage dueling a Fire Mage. Who won?
Duh. *I* did.

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I walked into Whiterun and had a guy run past me out of town, followed by a female NPC wearing only a hat, gloves and boots shouting "thief" chasing after the first NPC. I guess the thief stole the clothes right off her back.
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Whilst fighting the dragon at Autumnwatch Tower, I managed to power attack my way onto it's back. It took off into the air and bucked me off when it went on a bombing run after Brenor. I flew all the way to Solitude and died when I slammed into the side of the arch.
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While exploring the regions north of Winterhold, I was attacked by some skeletons. Now, skeletons are pretty weak and my power attacks usually make them explode rather violently. I was pretty far from the College at this point, but I could still see it off in the distance (nothing but a silhouette though). I found a dungeon, went through it and then went back to the college to sell things. When I got to the door to the actual inside of the College, one of the skeletons' heads flew down from the sky and struck my character in the back of the head, dealing almost lethal damage.
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While walking around the area outside Whiterun trying to mark off every location I could find, I saw a mammoth spawn in the air and fall to his death several hundred yards below.
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The only time I have seen two dragons at once (other than in parts of the MQ), they were fighting each other.
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The one time I finished a dragon off in the air (using a spell), it fell right on me and killed me.
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http://www.youtube.com/watch?feature=player_profilepage&v=7Op-cVgb7WU