Most heat-resistant brakes?
Hope V2 with the vented rotors. They were developed for and tested in the Alps. So far, I've only had two hours of descent on mine, dragging most of the way to keep myself from going off the side of the mountain, but they did not fade, didn't pump, nothing.
-Larger caliper body (higher oil capacity)
-Wider window for the pads to receive and vent cooling air
-Different lever body in the Motos (much higher oil capacity, now using tech levers for 2009)
-Vented, two-piece rotor. The venting is obviously for cooling and heat capacity, but the al hub carrier also allows the rotor to expand and contract when it heats and cools to reduce warping. Some have claimed it helps pull heat from the brake track. I don't know, but the transverse webbing does get very hot.
those..and probably Magura Gustavs...