This one is special to me because it was nearly lost, but became one of my favorite customer service stories.
I shot it on Velvia (E-6 chrome film) but it was accidentally processed as C-41. When I went to pick up my order, they explained the problem, and showed me to the back where their digital technition has scanned the negative and was adjusting the colour. We sat together for about an hour tweaking this, and nudging that until it looked as close to right as it was gonna get. Then they shot off a few 4x5 chromes from the digital file, processed them immeditaly, and a few hours later I had my project turned in on time.