A few months back I was having a discussion with some friends about airline security, my favorite dead horse to beat. I mentioned that despite the TSA's fascination with small, pointy things, I could easily make a soda can into a weapon. Take an empty can, twist and it unravels to reveal an edge about 12" long.
So I drag my thumb lightly across the edge while explaining how sharp the edge is, and when I pull my thumb away I'm bleeding...
Point made.