Most daring thing? I think I might have a tie. First one would be back when I was in High School. My mother had found out about my liking of diapers and decided I needed to go see a psychologist. The day of my first appointment came, and my mother told me to go upstairs and get dressed in some appropriate clothes. Deciding to stick it to them a bit, I took what she said to the letter, and dressed up in some loose slacks, dress shirt, and a Double Abena X-Plus diapering. Pulling on my jacket, we went off to the psychologists. Best part? Apart from possibly the psychologist noticing, neither my mother, my step father, or any of the other people in the waiting room knew.
Second one was in college. I'm a fan of absolutely SOAKED diapers, to the point where they're so swollen that they force you to waddle. So, one evening when both of my roomates were passed out in bed, I went to the common shower, diapered up in a Abena X-plus, and showered. Then, dumping a decent amount of conditioner down the front, I got out, dried off, then taped on a second abena x-plus and pulled on my plastic pants. I must have done the fastest waddle/run down the hallway to my room, then the slowest as I made my way past my roomates and climbed up to my bunk. Once there, I settled down, enjoying the warm, soaked diaper. Then, IT happened. One of my roomates started talking. He was awake and on the phone with his girl. I don't THINK he heard the crinkling, since I was really slow. If he did, he never said anything.
Anywho, those are probably the most daring things I've done in diapers.