I always enjoy going with someone on their first trip to World of Coke in Atlanta and telling them to "try the Beverly, it tastes delicious" then watching their reaction. What I find amusing is that the Beverly drink was discontinued in Italy (in 2009, according to Coca-Cola), yet it still shows up at World of Coke, Epcot, and other places with Coke tasting stations. It really is a terrible drink, but a must-sample for anyone visiting a Coke tasting station for the first time.
As for why Coca-Cola merchandise has appeal, I think Grand Admiral hit the nail on the head. Coca-Cola has been very clever with their advertising from the very beginning, and made Coke products more than just a drink. They became a part of the pop culture.