What is the funniest thing a doctor has ever said to you?

I had a good rapport with my (now retired) General Practitioner. Once, I went to see him for food poisoning. It was campylobacter and he gave me antibiotics. They worked but I got clostridium dificil from the antibiotics and he said I had to take Vancomycin, the antibiotic of last resort.

I asked what happens if it doesn't work? "Well, Scott, then I'm going to have to take you out back and shoot you." He said it so calmly and dryly that I couldn't stop laughing.