With my mainly unthrottled diesels I usually run a bit of fuel through them before the first flight of the day to wake them up and to establish the settings for the conditions.
Today I ran up the super spitfire fitted to my Bantam and decided as it was nearly flat calm I could afford to back it off a bit to give a nice gentle climb out, momentarily distracted in stead of reaching over the prop to back off the compression I put my fingers straight through the prop arc! result a bloody sore finger and a broken vintage wooden propeller, hate to think of the outcome if it had been one of my more powerful engines....learned a lesson today!