My most embarrassing moment also involves taking a header, but I can't use the slick or sticky floor excuse.
I was trail beside the ballhandler bring the ball out of backcourt with no pressure, just jogging up the court. I guess I didn't pick my feet up enough and caught a toe and took the big dive. I am a big guy and have a long way to fall. That, along with the fact that everybody saw it since I was right next to the ball made it worse.
The best part is that I looked at it later on tape and it appears that I tripped right over the midcourt line. Gotta tell that school not to put the paint on so thick!