This is a Cristate or Crested Saguaro. These are fairly rare, occurring in only about one out of 200,000 Saguaros. It is a mutation for which the exact cause is unknown. This particular one is near Organ Pipe Cactus National Monument. I was driving around 65 mph when Janet suddenly yelled to stop and turn around as she had spotted this rare Saguaro. So, I stopped and went back, and we hiked over near it and got these photos.