This may read like erotic fiction, but it really happened to me.
When I was 19 I went to the Doctor for rash on my leg. He checked out my leg and explained he needed to see the rest of my skin to better diagnose what I had. I stripped to my briefs as he watched. Then he pointed at my briefs and made a downward motion with his finger. I understood and dropped my briefs as well. I was a little embarrassed because I had only recently begun to shave down there.
He sat in his exam chair and motioned for me to step closer, closer. I was standing with my cock only a foot from his face. With a very stern look he began to inspect. He asked if I ever had issues with jock itch. I replied that I did occasionally. He pushed my cock and balls to the side to inspect, and then grabbed the head of my cock between two fingers. He moved me from side to side, and up and down. The friction was having the inevitable effect. I got hard, and fast. He told me I must be a horny little guy to get hard that easily in front of another man. I was embarrassed as hell and wished he would stop. He pushed my now hard cock up against my stomach and commented on how I was larger than average since it almost reached my belly button. I turned around for him to inspect my backside, and then he told me to dress. I was prescribed and ointment and he set up a follow up visit.
I spent the next week thinking about what had happened. I was a little ashamed, but a little turned on by the unorthodox exam.