Was relocating a $10k piece of networking hardware and dropped it into another 10k VM server. Server was fine, network hardware was not. It was during a project that was a real mess, thought it was a stupid mistake though.

We were able to work around it, though we did lose the contract we were trying to make. Honestly though given how rushed and panicked that whole three months was though, we were lucky nobody suffered anything worse. Real shitshow.