walking advertisement

Another, more prosaic term for fanboy. Also a clinically documented disease or syndrome, whose symptoms include excessively trying to get friends/family/strangers to partake in a product, espousing the many wonders of said product, and turning into a hell-spawned daemon when someone says that aforementioned product is shit.

Person: You should play FoRtNiTe

Me: Stop being such a walking advertisement.