At first it was my oldest pair, the headphones that started it all for me, the Sennheiser HD212 Pro's. He severed both left + and - wires. Fortunately I could fix those (but the OFC doesn't really apply anymore, so there's that nagging in the back of my mind), and what a PITA that was!
Yesterday it was my Sennheiser CX380 Sport II. He severed just the right - this time. There's no way I'm going to attempt to fix these, I'll have to replace them.
What a jerk!