Nobody.
Good Will Hunting is a pretty good movie with some flaws, including Robin Williams' painful attempt at a Boston accent.
About the only actor that got it right in a movie and wasn't from Mass. was Johnny Depp in "Blow". The guy nailed it, in my opinion, because
he figured out that we tend to slightly de-emphasize the famous "ahhhh" sound, especially when there are two Rs in a word. Hah-bah (harbor). You take a little off
the second syllable. Everybody else thinks about it coming, gives it a little too much "ahhh" and it never quite sounds authentic.
Mark Ruffalo was really good in "What Doesn't Kill You", too, but nobody saw that one.
Speaking of prom night, there is a great local comic named Christine Hurley who does a good bit about her Honeymoon.
She and her husband were staying in a bungalow on some Caribbean beach feeling like she
was really in an exotic port o'call and preparing to get busy when a female in the one next door
started yelling "Fuck me hahdah, Mahk!!!!" ......and that totally killed the mood.
However, that accent was recently ranked as the 2nd sexiest in the US (trailing Texas). The Providence twang
ranked 38th, although I'm sure BeagleBay has a legion of fans down the Cape.
cajuns
