Well, I had babies at home without any pain medication. That was pretty uncomfortable for a bit, but very exhilarating, too. I felt like I'd won an Olympic event AND gotten a baby as the prize :) One time I got stitches afterward, also without pain meds. Sounds dramatic but really not even in the top ten, discomfort-wise for me.
The most discomfort I've ever endured was being a foster parent for a year to an infant we knew we would not be adopting. We cared for and totally loved the baby every day of his life until he was adopted, knowing that he would be leaving us. When he left it was more than discomfort, it was agony. But for a good purpose, and totally voluntary.
What else...tattoos, sleeping on the floor/other hard surfaces for months at a time, not using sweetener, not eating after 6pm, no AC for several years...these are things others have seen as discomforts, but didn't usually register with me as uncomfortable and were just part of meeting other goals.