It happens to everyone at one point or another. You are the hired photographer for a wedding, birthday party, go-kart championships, etc.
Yet there is always someone with a DSLR (usually a Rebel with the kit lens and annoying pop-up flash using the multiple-flash red eye and AF-assist feature that's annoying) who thinks he/she is a professional photographer and gets in the way, or even someone with a point and shoot who realizes his flash is not strong enough, so he gets right up into the action.
My example: I was the hired photographer for the couple's wedding. The bride pushed cake into the groom's face and I had no angle whatsoever to get a shot of it as the guest photographer was in the way.
I'm sure she got a nice picture of the groom's face along with her hands in the picture. Wait, maybe she zoomed in and got a nice crop picture of just his face. *FAIL*
Let's see what you guys have.