Not that many years ago I was on a campout with the Troop I worked with. We were playing a game, Capture The Flag or something like that. Next thing we know a Scout is trotting into camp obviously in some pain. Turns out he slid down a embankment, maybe 15 feet or so right into a cactus. Considering we live in the desert this alone would not have been that big of a deal, except he slid into the cactus open legged. The Scout spent about the next hour in his tent with tweezers, removing the cactus spines from a sensitive area. The next morning he was fine, but of course we did have to alert his parents encase an infection or anything set in.
The lesson.... if you are going to slide down a hill into a cactus make sure you don't damage anything important.