What a great guy! - and what a beautiful little market. This is the kind of place that makes city living worthwhile, and the Rosi Square neighborhood such a surprisingly civilized and comfortable part of Boston. Don't be shy about introducing yourself as a new customer - Tony is sincerely warm and friendly.
I agree with Katie's review that Tony's sausage is great - worth dropping in for by themselves (they freeze well too). He carries the basic cuts of meat, and he'll custom cut as well, although if you're looking for something big like a whole butterflied leg of lamb, it's essential to call ahead. His meats are very good quality.
As far as the standard Italian deli meats/cheeses (ex: parmesan reggiano, prosciutto, linguica, etc) - I find they're always available. And if anything, he carries so many different choices of Italian dry/canned goods that it can feel intimidating at first. But it's all of superior quality and pretty darn close to supermarket prices
The store is not open on Sundays or Mondays (like many small businesses in Rosi Square... or Italy). But Tony's nephew is helping him out these days, so the stores hours have re-expanded a bit for the rest of the week. In particular, he's open on Saturdays for a decent chunk of time, which I find very useful during the summer when the Saturday morning open-air farmer's market in Rosi square is around. Some sausage from Tony's, some basil and a few heirloom tomatoes from the farmer's market, a loaf of fresh peasant bread from Fornax - the makings of a Tuscan feast! JF.