I gave blood a few times. When I was in the military it was a regular thing (during Vietnam). Then when I moved to where I live now, a very rural area, there was need so I again volunteered. They looked really concerned after the first time and they seemed to hover around me. The second time, as I was sitting there eating my FREE cookie and drinking my OJ, the person in charge came over and sat down.
She said, "How are you feeling?"
I sez "Fine. Why?"
She sez - you're as white as a bleached sheet. Listen - you make us really nervous. Would you mind not giving blood any more?"
So now I don't. (I apparently have a sensitive vasovagal response?)

I've never thought of myself as a scary person before - but I guess that's what I am. Feel the POWER! I can scare a whole room full of RNs!!! ;-D