One of the more difficult is probably Nassarsuaq Greenland on a 757. 1800 m Rwy landing with a downslope of -2.7% and the Rwy overrun would put you in the ocean. That was an interesting one as well.
Yes, and don't even think about it in winds over 25 knots (which are very common) the turbulence created by the air falling down the glacier is absolutely brutal. I once watched a DC-8-63 almost come to grief at BGBW.