My arm.
Last time I gave blood it all went fine and I went to get my juice and biscuits and my arm started to bleed again, all over me, the floor and the biscuits. Today I went, all went fine, I was about to sit down with the juice and biscuits and then my arm started to bleed again, all over my sleeve, my jeans, the floor, the emergency couch but luckily not the biscuits this time.