Surprised, but enjoyed it.
I went to our local park recently to use the walking trail there, but before starting I went to the restroom close to the trail entrance. While in there I was standing at a urinal when another individual walked in and stood at the urinal next to me. He looked like he was about 30.
Soon I noticed that it looked like he was playing with his cock and when I glanced over, could see that he was masturbating. I continued to watch and he turned toward me so that I could see what he was doing better. He had an average length circumcised cock, but it was the thickest I had ever seen and his cock head was really huge. It looked like his hand couldn't go all the way around it!
I got turned on watching him, so I began masturbating my uncut cock. I always start by playing with the foreskin and not retracting it. Then after I am fully excited and getting close to coming I retract the foreskin all the way back over my cock head. The only thing he said the whole time was that he loved looking at an uncut cock and that it really turned him on. We didn't touch each other, as he just wanted to be watched and to watch me. It wasn't long before he ejaculated and I couldn't believe how much cum he shot, also how far.
I returned home later and jacked off again, reliving watching him jack off his thick cut cock.