Things you can say which will reliably discomfit your patients:
For patients who will need surgery:
- "There's no cure for what ails ya except cold hard steel."
For patients upon whom you are performing a procedure:
- "What the hell is that?"
- "Hold still, I'm going to try something."
- [To Nurse] "How does this gadget work?"
- "I've never done this before, but I'm pretty sure I can pull it off."
- "Now this may hurt a little . . . actually it's going to hurt rather a lot."
For patients with a medical diagnosis:
- "There's Good News and Bad News. The Bad news is you have [X]. The Good news is that it's you and not me."
- "Everybody's got to die sometime."
Now, I've never said (most) anything on this list, but I have a wicked mind and have thought about it on many occasion. I'm sure you have thought about it, too. Feel free to add suggestions in the comments.