One of my more memorable experiences.
My friend Mike (not his real name) and I were masturbating together in his dorm room. As he had only one towel out of the wash, we were kneeled side by side but slightly facing each other, both of us masturbating dry.
As usual watching him push his foreskin back and forth over the head had me envying his foreskin, wishing I hadn't lost mine. But my cockhead was swollen and very smooth, as it looks only when I'm very aroused, so I was definitely still enjoying myself. About 15 minutes into the session, he grunted, 'Here I go.' A few seconds later, ropes began to squirt from his penis as he continued jacking with shorter strokes.
One of those strokes went a little wild I suppose. His third or fourth shot flew almost sideways and as I pulled back during a stroke, it landed stretched from the end of the shaft where my hand met it, and over my cockhead. Before I could react, my hand was already making its return up my dick and the cum spread all over my cockhead making it extremely slippery which caused my hand to slip. The first thought I had was about how hot his semen was to the touch. The second thought, but there wasn't one. I orgasmed at that moment. Usually when I come, I stop stroking for the first few shots, then slowly speed up again as the orgasm subsides, and I never stroke over the head to avoid getting my hand messy. This time, however I was completely out of my mind from the unexpected orgasm and continued to stroke even as my semen fired.
My hand and the towel were covered in our loads. I let out a long breath. He looked at me, said 'oops,' then dipped his still hard penis head into where most of my load had landed and spread it around. 'Fair is fair.'
We were both still hard, so we masturbated a second time.