Have taking small rocks to the helmet on climbs many times. But here's when I wish I had a helmet on. Was shoveling snow and ice on a 2 story roof in February. Had everybody anchored in and had to remove about 4' of snow from one large storm on a 80 x 30 foot roof. There was a valley where 2 opposing roofs met which creates a huge ice dam right in the middle of it. I was removing snow from the dam, when one intelligent individual used an ice pick above me. This fractured the ice and immediately caused the entire roof to slide with me still standing on the ice. After taking a 2,000lb, 12" thick sheet of ice to the head I was left dangling upside down on a rope. One concussion and a few displaced vertebrae later, I really wish I had a helmet on and that I had stopped the genius from digging above me.