OK, running wire for invisible dog fence along my stonewall through the woods. Hunched over, tucking wire under bottom rocks. Rock on top is loose, rolls off of wall, over long dead cedar sapling... sapling bends to the ground under weight of rock, rock rolls off and sapling springs back and smacks me right in the mouth...
Just like getting whacked with a broom handle...
Elapsed time from rock moving to impact with face, about 1/2 second.
Hoping to finish the project if I can convince my lip to quit bleeding
edit: Ice Cold Beer bottle works better than ice pack, and tastes better too!!