I haven't actively looked for hookas, but if I was ever in the need to buy one I would likely come…read morehere and check theirs out, because I haven't really seen many around the center.
They have not just the basics but a pretty decent assortment of cigarettes, cigars and pipes. In fact, when la Castellana is closed for a month of vacation in Ferragosto (the specialized cigar and pipe shop on the back of the duomo), he sends his clients over to this tabacchi!
They always have unique gifts/souveniers on display, and altough they are a tad pricey, you gotta give it to these guys cause they are in the center right in front of the duomo!