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For burgers, I am a big fan of R.F. O'Sullivan's in Somerville. I think they are better than Bartley's

I totally agree that Brown Sugar Cafe is the best Thai in the city, but sadly, they're closing!

I was also disappointed not to see Picco (513 Tremont Street) mentioned anywhere for pizza or otherwise. If you like a well done pizza, Picco is where it's at. My personal favorite is their chanterelle and leek pizza (although I don't think that's on their permanent menu, but if they have it definitely definitely try it)! Their arancini are to die for, as well as their warm spinach salad with pancetta, white beans and goat cheese. I have re-created this salad many a time, and it has quickly become a favorite of mine. They also make really wonderful homemade ice cream (the caramel swirl is my favorite, and the the dark chocolate brownie sundae is sinful) and italian soda.

And finally, best Tapas, Toro (1704 Washington Street). It may be crowded for dinner, but it's worth the wait! I recommend the patatas bravas, the chicken and potato empanadas, the grilled corn (this is a must), and of course the paella.

I know I'm a little late to the table, but this is an issue that always gets me wound up and I just wanted to add my 20%

I was a barista for years, at an independent coffee shop and I depended on tips to survive. My minimum wage salary barely covered my rent and utility costs, so my tips provided me with food and other essentials as well as funds non essential items and activities which a person needs from time to time. To me a barista is no different than a bartender, they just serve different kinds of beverages. And I would assume that most people tip their bartender, even if all they are ordering is a bottled beer.
I actually labeled my tip jar "Karma Jar" and with the exception of one Hindu woman who found it offensive, people were very responsive to it. I always tip at least $1 esp if I know the tips are being pooled.

I also always tip the pizza delivery guys. They may get paid more than server rate, but they have to use their own car, and making frequent short trips does add to the wear and tear of any vehicle, plus buy their own gas and we all know how that's been lately. People have told me that it's not necessary to tip when a delivery fee is added to the bill, but more often then not that delivery fee goes to the restaurant, not the delivery guy. Pizza delivery can also be a rather dangerous occupation, for more info visit
http://tipthepizzaguy.com/
Which is a little snarky here and there but does give some perspective from the delivery guy's point of view

I have read the comments with great interest. I live in New Zealand and generally there is no tipping. If I take a taxi I round up the amount owing, if the fare is a straight $20, then that is what I give. That is the norm here. There is no tipping of hairdressers for instance, and you might tip a waiter/waitress after having received truly good service and on a special night out. That amount is given as a thank you but it is not expected. The minimum wage here is $12.00 per hour from age 16 and that is before tax. I can't get my head around tipping. I feel that a working person ought to receive a "proper" wage and should not have to rely on tipping (people's mood etc etc) to make a living. Let the price of the meal reflect the true cost of that meal. Having said that, should I travel to the States, I would make an effort to find out how to tip correctly but I would prefer not to have to think about what is appropriate to give and suffer embarrassment through ignorance.

If you ever leave less than 10% for ANY reason - you are a thief. By federal law at least a 10% tip must accompany all service transactions. The problem with the law is that they punish the victim. You see, whether you tip or not Uncle Sam still taxes the server for a 10% tip, thus making not tipping a crime. The server pays a fine for a bad tip in the form of income tax. So when you do not tip you are actually taking money they earned from other customers. That makes you a thief. If the service was not up to par, speak with the manager. If you do not speak with the manager but leave a poor tip the service wasn't bad; you are just cheap. And to be quite honest if you get any food, be it what you ordered or not then the server has earned a 10% tip.

I am a good tipper, WHEN my server is good. I believe that just like a bonus at other jobs, extra tip is all about how you work. For satisfactory service I'll give 15%. But, if the waiter is rude or ignores the table, I don't mind tipping less that that. I'm a reasonable person . . . if they can't figure out what they did wrong, then they'll probably just do it to someone else.

Once while tending bar at a smallish neighborhood pub, a gentleman seated at the bar left a few bills on the bar for me and went out the door. The man seated next to him, wide-eyed, snatched up the money and followed him out the door yelling "Hey Mister. You forgot your change." (Several other patrons, and me, watched open-mouthed). Shortly, the man returned, put my tip back on the bar and muttered something like, "he said it was for you."

I work in a very upscale bar and restaurant in Southern California. I personally think that most people don't tip as well as they would if they knew what goes on with their tip after they leave it. A server in our restaurant has to tip out 5% of their sales to the expediters (the gentlemen who keep track of the courses as they come out and deliver them to the tables...these are the guys you see who don't actually take your order or reccommend wine to you, but can balance five plates on each arm). Then that server must tip out the same percentage to their bussers (who are resposible for clearing, keeping waters filled, bringing bread and butter, etc). Then the servers must tip out their bartender, based upon their liquor sales figures (that's me..oh, and then I also must tip out bussers and expediters for bringing and/or clearing any food consumed at the bar). So say the bill is $100. That's $5 to the bussers, $5 to the expediters, another few bucks for me if the diners drank...and if the diners left 15% ($15), the server is keeping a few bucks.
Granted, this is a problem. And it becomes more of a problem because then a server feels cheated and doesn't tip out internally the way s/he should. So things happen like that particular server's food always seems to come out a bit late, or the waters don't get filled as promptly as they could, or the drinks seem to be a bit weak...and then the cycle begins anew with the leaving of a smaller-than-average tip.
I don't know the solution. I know I'm irritated when I make drinks all night for a particular server and I get three dollars from them at the end of the night while they are claiming "bad tippers". But I know the servers are irritated at having had sales figures on food totalling $1500-2000 and walking out of the restaurant with 80 bucks. Maybe if we were salaried, this wouldn't be the case. But a lot of bartenders and servers I know do these kinds of jobs for the cash...there is an attraction in being able to put one's paychecks in the bank and never touch them because there is always cash in the pocket. Having served and bartended for years, I am a good tipper...quite good...but with the internal tip-out system varying from place to place, even I don't know if the tip I'm leaving will come out accurate for everyone in the end...and I can't afford to start tipping 40-50% across the board.
Phew...what's to be done?

@wunami....bitter much? you chose the career to help people? or to get money? just wondering. yes, I generally tip at or above standard for regular service and above and beyond for great service.

I tip as much as I can to anyone who serves me. Just came back from a very splurging vacation where I tipped doormen, baggage handlers, concierges, waiters, captains, hair stylists, shampoo people, cab drivers. As far as I can remember, all had started out giving good service, and all continued, with maybe a little added warmth, if I saw them or used their services again.

Big tipping is a nice thing to do, and good karma, if/when you can afford it.