I was hit head on by another cyclist on a bike trail once... she'd been looking down (I think looking at her feet, perhaps trying to clip in) and drifted onto the wrong side of the trail right around a corner. I came around said corner and encountered her handlebar to handlebar.... fortunately I was not going super fast. I tipped over into a wall that was on my right and sort of slid down it. The shoulder strap from my messenger bag slipped down my left arm and trapped it to my side... so there I was, both feet still clipped in, right arm trapped against the wall, left arm pinned to my side by my messenger bag - I was totally immobilized... Poor lady was mortified, her friend eventually helped me up.