Two guys come to mind.
The first one, I saw him in a gay sex shop in my area, which I frequented very occasionally out of curiosity when I was young. There was also a backroom. Admission was free for those under 25, I took advantage of that.
I went there to watch. The establishment had a small 'cinema' room, where pornos were shown continuously. There were never many people there, a few guys who came to jerk off and leave so quickly.
One time I went there and there was this guy, mid 40s, bearish, hairy, bald, bearded, a bit overweight. Not handsome or ugly, just average. He was sitting, legs wide apart, with great ease, and above all a huge dick. He had a solid erection and he was slowly jerking-off. To give you a size comparison, almost a regular box of Pringles crisps. I was not the only one but as he saw that I was looking at him, he asked me what I thought of it. I was quite intimidated, I said without originality 'it's huge'.
As the conversation progressed, he said that he was not gay, but that he regularly comes here for exhibitionism, reactions and compliments. He claimed it was 25cm. He asked me if he could see mine, I accepted. It made him very excited. He was very excited after that but he didn't want anyone to touch him.
The second one is more recent. I have a small leisure cottage, not far from the North Sea. In the parking lot of a supermarket, there was that homeless man, that I see occasionally, maybe a migrant since his ethnicity and the area (many want to go the UK). A young man, not very lucid, and he has a habit of pissing without worrying about the gaze of passers-by. I don't know if it was a semi or not but it was clearly huge, a bit thin but very long. He shakes it frantically every time he's finished. He keeps touching his crotch through his sweatpants otherwise. Since he was insistent when begging, and due to customer complaints, the store made him leave. But I still see him around.