As usual I'm quite late to the party. Just discovered this thread on my day off from work.
My choice was made many years ago after watching a Vuelta stage that took place amongst rain and fog. I was about to begin posting on the bicycling.com forum and that stage (what limited coverage that was available due to the conditions) came to mind. Some of my favorite posters on that forum at the time were Alpe d'Huez (yes the same one that is a moderator here), Gavia (now an administrator at Podium Cafe) and a very wise Koppenberg (no longer posts there). Being a fan of Spanish climbers I chose Angliru. My avatar has changed multiple times of course and I've recently gone from one that I found quite entertaining of Samuel Sanchez at one of the Tour route ceremonies looking introspective with his hand on his chin to my current of Juan Antonio Flecha, which just may be my favorite of them all.
My signature is a tribute to the current best climber in the world, and an example of the fear he puts into his rivals when he attacks.