For me it had to be Megeve, in France. 4800+ft elevation, 400m runway, with 102ft upslope, tight in a valley.
...oh, and I forgot the 3000ft cliff facing you as you land - it's just a couple of hundred metres beyond the end of the runway - one way in, one way out. Go-round? I think not! It's arrive-or-bust flying. Just thankful I went in a heli!
Holly Copter.