I know many other people have said this before, but...
About to FUS RO DAH someone off a high cliff
Whirlwind Sprint off said cliff

When Lydia was crawling on the floor with 1% health and i missed my warhammer swing and hit her in the back of her head

This happened to me. I thought I had to save up a large number of souls before they automatically unlock from greyed out state. Basically my first character got to level 50 had already beaten Alduin, became Arch Mage of the College and I was Listener of the DB as well as Harbinger of the Companions. I had saved around 30 ish dragon souls and I still couldn't figure out why they weren't unlocking. And I was getting so frustrated that I couldn't find the answer on the UESP. Finally around my 33rd dragon shout I believe is when I opened up the shout and realized they had to be unlocked using the X button........................

I never made that mistake again.

Done that many times. I need a keyboard that can disable those button combinations while playing.

Exploring a dwemer ruins with candlelight spell because it's dark, when I am about to open a door the light went off, dual blade came out of the floor and killed me instantly. I activated traps in the dark,

"One last strike and you are off to Sovngarde you damn cryomancer!" *BAM* Oops.. Lydia, how many times do I have to tell you to not get in the way while I do a power attack? *open console* *types resurrect*

well, i was artfully dodging those swinging gates and swinging axe traps when i seen a lanturn hanging from the ceiling, couldnt be anything deadly about that! i was interested so i walked up and stabed it with my dagger, hope the draugr like deep fried argonian.

When I first saw the oil slicks on the floor, I thought they were maybe a scenery touch, and my mage ran up to one of the slicks to close the distance between him and another enemy mage, so that I could hit him once with a paralyzing poisoned dagger before I finished him off.

I accidentally lit the floor on fire because I left-clicked rather than right clicking (probably should've unequipped my fire spell first). Wasn't pretty.

Hey check out this moment http://www.youtube.com/watch?v=3s5dfwYw41o&context=C3e59cd2ADOEgsToPDskJodZG9BVp6ngJsGftZ-o3k

I was stuck in a random dungeon where there were bars sectioning off the rest of the area. I probably spent about 45 minutes combing every inch of this place looking for the chain to open it but I couldn't see it for the life of me, admitted defeat and Googled it just to check it wasn't a bug (fully expecting it to be, seeing as I thought I'd looked everywhere).
First search showed up a forum post by a guy having the exact same problem - only for people to point out it was right next to the bloody barred door. It wasn't a puzzle, bug or even well hidden. At least I wasn't the only one having a serious derp on that one.

Also whenever I jump over a crest of rocks only then to discover it was the edge of a cliff. When will I learn to look before I leap FFS.

Using Whirlwind Sprint while scaling landscapes faster.
Was on mostly flat ground with a few rocks.
Accidentally sprinted off of a cliff....Noticed the waterfall far to the right of where I fell from in my death camera.
Didn't see it or the flowing water due to not being close enough.

o_o

Lesson learned: Don't sprint around all the time.

everytime I think I can make that drop/fall, but then I break my legs and tumble down the mountain...

happens once or twice per play

It another misplaced..er misused shout..I healed the traveling bard..and he turned hostil..I kited him to the tallest waterfall in Skyrim and was gonna Fus him off..when I sprinted myselff of the damn falls..I think the game said "Ohhh yea hes dead" cause halfway down start menu popped up as soon as he hit the water...long story short..dead on impact of water..the bard..survived..WTF!

Charging into a witch coven . . . and then getting my burning corpse immediately thrown back by a barrage of spells.

I just got stuck under an iceberg and drowned.

****POSSIBLE SPOILER****

Thats nothing...On the thieves guild quest at the brewery..just put the poison in the vat and the game tells me to go out the door. I click the door and i am told i need a key. I spend ages looking for the key, I go back down the tunnel to see if its in a corpse or a container but no its not there. I go back to the room and search there looking under,in and behind everything nothing....So i stood in front of the door put my controller down to make a drink. I come back nudge my thumbstick slightly and my character looks at the side of the door and low and behold theres the bloody key hanging on a hook

When i spent quite a heck of a time searching for the answer to the puzzle in a dungeon; i examined the circular patterns on the wall, i examined the doors, i examined the positions of the light sources.

Only to find out the answers were printed behind the rotating animal pillar things.

Z was the "Grab Item" button in Oblivion. Z is the Shout button in Skyrim. "Ok, I'll just move this over here... FUS!"

Last night, a flame atronach attacked, so I moved in to fight her. Behind her was a guy glowing with magic, so I sort of assumed he was a mage and had conjured her. I killed him. He was a priest of Stendarr. The atronach was attacking him.

Classic. My first death was a D'oh moment. Going through Bleak Falls Barrows on my first character, watching TV at the same time, not noticing the floor trap to release the death gate.

Biggest 'Doh moment for me is traveling through a Dwemer ruin with Mjoll.
I gave her most of my good heavy armor and 2handed weapon (I'm a light armor + sneak character, so it doesn't matter in my case).

When all of the sudden 3 or 4 bandits attack, all wearing the same armor and weapon as she, and some looked like they were attacking each other.
So without hesitation I dispatched of the bandits, only to realize the only one left was attacking me; I'd killed Mjoll by mistake. Oops.

Ive done that too

OH my! I did this in my home in Whiterun! I lit my chair on fire. was so funny!!!!

I cast Fus in my little Whiterun house. I reloaded, because the item exploding bug would have left every surface in my home bare.

*****DWEMER SPOILERS AHEAD********

Just last night doing that damn Lost Expedition mission in the Dwemer City underneath Markarth. Found Stromms journal, fought ten thousand spiders and falmer and centurions and mechanical spiders and whatever. Then I had an objective saying find someone alive who knows about the expedition, so I look where the arrow is on the local map and it ends up behind this wall I had no way to get to, THREE HOURS I try and get to it, every room I look for a secret passage or something but nothing.

In the end I thought screw this and worked by way back up out of there, as I'm going out I notice that Calcimo dude has a big whie arrow above his head. GODDAMMNIT I didn't know it meant go back and talk to the bloke who gave you the quest, I was looking for someone in the city itself all night!.

My mate had a good one, always he was complaining about the game being so hard, raging like hell on the mic, I was like I'm not getting it I've just put it upto expert are you using perks that don't suit your character?. He goes quiet then a minute later Pete, your not gonna believe it but after 23 hurs I've just worked out you dont get those perks put on your character automatically. No Meist, not hard to believe at all mate.