i've used my head a few times. (dangerous when loaded hehehehe)
I did pull my ulock once (car tried to run me down, guy got out started chaseing me around the car (never flip off the car behind you...)
But i was smart and kept it hidden until i could get away (bravery aside i pick my fights and always think about that knife and gun...)
Pulled it the other day and waved it for effect (guy cut me off, forced me left into traffic then yelled at me, reved the engine then i moved to chuck the lock (then dive to the sidewalk) and he hit the brakes.
One thing i wish i had was a James Bond combo oil slick and tear gas/ smoke screen...
And a Bond girl on the back of my xtracycle...