Doyle's Cafe

Doyle's is a true neighborhood bar - you see old-timers, sports teams, couples, families - pretty much everyone from the diverse JP neighborhood hanging out at Doyle's. Food is consistently good, large selection of beers not commonly offered - but they have been at Doyle's forever. (It's 125 years old!)
Doyle's is famous as a stop on the political trail - all the old pols stopped by. You can see that reflected on the walls throughout the rambling rooms that make up the place. It's also used in the movies as the "quintessential Boston Irish bar". It was in 'Mystic River' and 'Bachelor No. 2' just filmed there in September '07. Also, actor Mel Gibson was spotted at Doyle's in August '08.
Can't recommend a better place to have brunch/lunch after visitng the Sam Adams brewery tour down the way. Or to watch the ball game with a friendly crowd (providing you root for the home team).
And they have their own generator, in the advent you are a JPer who experiences a power outage during a blizzard! Stop by on St. Patrick's Day for one of the area's biggest celebrations (bagpipers perform throughout the day).