I have two, actually.
The first "celeb" cock was a famous pianist whose family emigrated to the States from Cuba. He's most renowned for his work on Enoch Arden and with the Moscow Conservatory. Anyways, we chatted on gay.com while I was staying with my dad in Florida on summer break from college in 2003. I drove out to the rural town he lived in, picked him up from the gym, and we went back to his house. We talked for hours, and then started fooling around. Incredible kisser, fantastic body, and a massive, so black-it-was-almost-coal-black cut dick that honestly scared me. Had to be 10", and 7" or more around. Cut, huge flared mushroom head. Couldn't suck it properly, but he fucked my brains out after a lot of very intense rimming. We made tentative plans to see each other again, he invited me to a show in New York, but nothing panned out. Last I checked, he married a guy and they have a house somewhere in New England together.
The second "celeb" cock I encountered was three years ago, right around Easter. My condo mates were out of town, so I had our condo to myself for the weekend. A no-pic, no-profile guy hit me up on Grindr. Normally, I never answer those messages, but I did this time. He described himself, sounded very hot, and I (very stupidly) invited him over. When I heard the knock at the door and looked, I was staring a relief pitcher for the Chicago Cubs in the face. Fuck, was he hot. We had a drink or two together, then he proceeded to use half a box of Magnum XLs (which fit quite snugly on what I would guess to be about 8.5-9" of FAT cut cock and massive shaved balls) and spent the night. So much fun. Never saw him again, though, but I enjoy seeing clips of him play and knowing what's in that cup.