What is the most valuable thing you have destroyed in anger?

A couple relationships, but that's probably not what you're looking for. I used to have a much worse temper when I was younger. It can still flare up sometimes, but it doesn't happen near as often now.

Aside from relationships, I can't think of anything better than a tennis racket. And it wasn't that expensive of a tennis racket. Maybe a memory will emerge from the cobwebs in a bit, though.