My friendliest chicken ever is probably Sandstorm. As a chick, she would willingly hop onto my hands and as a hen, she insisted on following me around the coop as I tried to collect eggs. She's a Rhode Island Red though, and in my experience, they're not always the friendliest. Sandstorm is a unique little bird. I'd say Buff Orpingtons (when they're not broody) and Barred Rocks are the most consistently friendly breeds. Silkie hens are also usually very nice (when they're not Broody) although I don't recommend a silkie rooster if you're looking for a very friendly chicken.