BOSTON has the best cheesesteaks (we just called 'em "belly bombs" up there) -- lots of thin-sliced beef on a GRINDER (not a roll) with PROVOLONE cheese and green peppers and fried onions. drink it down with a "six-uh-sammy" from the "packie" or if you're still on duty, just a "tonic" (not soda, not pop -- TONIC).
SteveS: as far as seafood goes -- try Naked Fish in quincy or on north street, or better yet, go to the Legal Seafood on boylston at the Pru. they're chains, yeah, but damned good. the guy who started bertucci's pizza also started the naked fish places (they have a kind of latin tilt to the fish there).
otherwise, check out:
East Coast Grill (in cambridge, inman square)
Max's Deli (downtown) for the BEST lobster bisque ever
Rialto (at the charles hotel) - just GO there.
Union Oyster House (after you do the freedom trail)