The three scariest moments I can think of off the top of my head are all skiing related, and curiously enough all related to moguls.
Story 1)
Tuckermans Ravine [Mount Washington]. A little introduction to those that don't know Tuckermans Ravine. Mt. Washington is the tallest mountain in the Northeast US, and where the strongest recorded winds in the US have been. Tuckermans is a ravine on the side, about a 3 1/2 mile hike up the mountain.
I spent a good hour and a half working my way up the left chute with a friend of mine. We finally got to the top, rested a bit, and headed down. I was going just fine through the bumps, but my speed control is a little lacking when in bumps, as well as my stopping skill. I decided I was going a little too fast coming into the chute and my legs were starting to burn pretty fierce, so I decided I'd stop, take a break, and then finish the run into the bowl.
I turned against the fall-line in an attempt to slow down, but it was a little steeper than I expected, and I wasn't slowing down too much. I looked up, and saw the cliff face coming straight at me. Realizing that stopping basically meant smashing head on into granite, I made a decision to lift my left leg, and jam it down to lock in the best GS racing turn I could muster. As I flew by about a foot from the cliff my brain was trying to figure out how to get down if I smashed the wall, or even blew my knee out making the turn.
Story 2)
Devil's Fiddle, Killington. It was spring skiing, a few dirt patches here and there. Cruising down, my buddy is up ahead [same buddy as story 1]. He stops, looks back, and yells something. I can't quite figure out what he's saying, and I look up ahead. I see a patch of rocks coming up... rocks being on the top of the cliff midway down [skiiers left of the trail]. Once again we resort to my wonderful bumps stopping ability...
In a panic I guess I sat back on my skis a little bit. I ended up launching off a mogul, with my feet quickly orienting themselves above my head. Not wanting to land on the rocks on my head, I threw my head back and my feet forward.
Next thing I know, the tails of my skis hit the snow, my legs went to jello, and I came down on my side and slid to the top of the cliff.
My friend, on repetitive queries to ascertain my status, was responded to with a consistant 6 word response... "I DID A F**KING BACKFLIP!". "Yea, I know you did, but are you ok". "OK? DUDE... I DID A ..." you get the picture.
Never skiied Devil's Fiddle again.
Story #3
Sunday River, spring skiing in June. Been skiing pretty well that day, and by this time I had gotten much better at actually stopping in bumps. The steepest section was the first section, and we had found an absolutely incredible line to buzz down. My buddy went down first [same buddy BTW], I headed down second. Half way down that section, I must have let my legs get a little too relaxed, because next thing I knew I heard a pop behind me, and it launched me back forward. I finished up the section and stopped to try and figure out what happened...
As I ran through it in my mind, my vision started to get hazy, and I laid down. I continued to rewind the mental tape and I figured out what happend. I fell back, bounced off a mogul and came back up on my skis to finish the section. I hit the back of my right shoulder on the mogul, thus making the pop.
By this time the fainting feeling cleared up, and the black flies were driving me nuts so I got up to continue down. My right arm was in so much pain that I couldn't move it much at all, and I just worked my way down to the bottom and went to ski patrol.
"You pulled a muscle... here's a sling".
I decided to hit the hospital on my way home.
"You pulled a muscle, wear this sling for 3 days".
4 days later, talking on the phone laying on my bed. Laying on my right side with my head on my hand, propped up on my elbow, I leaned over to hang the phone up on the floor. My elbow slid, and "POP". That time I knew _exactly_ what happened, as the recoil of my body caused my shoulder to pop back into place.
16 dislocations and an inline skating career later... I had surgery to repair it. It's popped out once since then.
Lying there trying to figure out what was wrong with me, was probably one of the scariest moments of my life...