What is your worst experience at work?

We were building a tool inside our product with more than 30 people for about 6 months. And just before the launch we realized that no one needs it. We relied on our current power users' feedback and it turned out they just didn't want to tell us the truth and disappoint us because of their loyalty.

That's a heavy one: I was fired because someone wrote an anonymous e-mail to my supervisor that contained a lie about an ongoing police investigation of me