I had the rear wheel lock up on me once. Turned out to be a laptop computer stuck between the fender and the tire.
Moments later I realized it was my laptop computer, now somewhat bent.

05 speedmaster - 1100cc, 11:1 racing pistons, Carillo rods, thunderbike cams, ported and polished head, 2mm over intake and exhaust valves, Barnett kevlar clutch, scepter pipes, oversize manifolds, 45mm HSR's, TTP stage 4 firestarter