From locking my own bike to a section of railing when I had to leave it somewhere. The railing is pretty stout, but it was in a semi-secluded place and we all know you can hacksaw through a railing, so I decided heck, they're gonna have to hacksaw through two separate pieces of railing if they want MY bike.

At the shop, we got a Specialized Sirrus of some sort that has its rear rim nearly broken in half in two separate places, and this happened while it was inside its shipping crate. I have no doubt that I could easily finish the job with my bare hands and an ordinary scissors, since the tires are Kevlar-beaded ones. IMHO this illustrates the fragility of an aluminum wheel rim, especially when it's the weak link in one's lockup scheme. I'll try to snag a photo of it tomorrow.