Climbing a Grade III ice pitch on Coire nan Lochain, and watching my protection metres below pop out, knowing that we were climbing 'alpine style', so I was actually only attached to the mountain by my buddy's boot. I was facing a death fall down the slope of Y-Gully and then straight down a 500 foot rock terrace to the corrie floor. I realised that there was no one to get me out of this other than myself, so I took the risk and climbed the pitch essentially solo with no protection. I was totally shitting it. I got above the ice section and then completed the rest of the route also with no gear because it was banked out with snow. So the most dangerous thing I have ever done was essentially soloing Y-Gully in winter.