The 7 top baristas in the world are known as the Arcobaleno, each one of them have their own speciality.
Fon is the master of herbal teas and tea's in general. He's so popular that he has opened a school about teas.
Mamon charges the most ridiculous prices for his products but since he uses only the best of the best no one can complaint.
Verde makes his own hybrid plants of coffee, some of them with horrible results but the ones that do came out good are renowed as the best of the best.
Skull is known as the death survivor, using the most exotics ingredients from all around the world he makes the most extravagant coffees and teas, but they have almost cost him his life in many occassions.
Colonello and Lal are renowed for one of the best but most dangerous coffee in the world, no one knows what it contains but if you are not careful while drinking it you can die (aka you drink too fast, add to much sugar, add too much milk, wait to long for it to cool down etc), when asked why they made such a dangerous coffee they only reply "It's a test, only the best coffee masters will know how to drink coffee, we refuse to serve anyone else"
Reborn, is the master of all the drinks with expresso, and he had never had a disciple...until Tsuna.
Aria, does not use special ingredients or knows to much of coffee but whenever you drink one of her products you can feel all the motherly love in the world in a single sip. Also, somehow she always know what you will order.