Never, ever let someone lean their wheel against your leg while they are inflating the tire up to 100+ psi--especially if they have just changed a tube for the first time.
For just a split second, the thought entered my head "should I have this thing leaning against my--"
Bang. Snakebite. Blew the freakin' tire right off the rim.
My ears felt like they were full of cotton for a full 10 seconds before they started ringing... and I now I have a lovely welt on the side of my leg.