Or wait until he's not expecting it
and hit him with a metal bar.
( Flapjack I spay a little mare for you, Tue 30 Jun 2009, 8:58, archived)

or start crying and screaming that you're a haemophiliac and when he turns away in disgust
kick him in the back
( manolith hooray for me, Tue 30 Jun 2009, 9:03, archived)