Spent a week in BCN around Christmas this year. Most meals were at home with family, or completely unremarkable. A few were worth discussing.
* Quimet i Quimet was worth going.
There's nothing undiscovered about this place; you can tell it's made some popular American and Japanese guidebooks by the clientele. We got there 10 minutes before 19:00 on a tuesday when they open for the evening and there were already several groups of foreign foodie tourists staring at their smartphones. Our early arrival paid off with a prime spot at the bar - it's much harder to order from the back of the house, because you'll have to wait for someone to come around.
Montaditos of foie gras & black salt, smoked salmon & truffle honet, zamburinñas and caviar were standouts, as were the house beer and vermouth. (They also make a mean gintonic, with Fever Tree on request.) This is a third-generation family-run establishment, and most of the folks working there were born into the job. It's a very busy place, but by respectfully waiting for eye contact and responding crisply and promptly with our orders when acknowledged, we got great treatment. Our places were defended by the staff when others tried to elbow us out, and we were plied with spoonfuls of an advocaat-like boozy custard and a 2015 calendar when we settled our bill, which amounted to €50 for my better half and I, including several drinks and enough food that we ended up skipping our planned dinner later.
* Al Atlas makes fantastic sandwiches.
On the southwestern end of Rambla del Raval is a little shop mostly selling sandwiches. It's easier to see the crowd of locals lining up waiting for theirs than it is to read the sign - that's how I found the place, just wandering by randomly. This is the anti-Quimet, pretty much off the tourist map. I could see this place being intimidating to some - you won't hear any English spoken and not much Spanish or Catalan, but you will hear a lot of Maghrebi arabic - but don't be dissuaded. Go and order a chicken sandwich with everything. You'll get a substantial baguette with chicken, olives, lettuce, tomatoes, yoghurt, onions, julienne carrots and beetroot, french fries, (non-pork) mortadella, and harissa, for €3, and you'll like it. Stay in and have some mint tea with it if you like, or take it away and eat it outside. We went here 3 times in a week, and I still think about this sandwich several weeks later.
* Roca Moo was "international rich person food."
Worth going to have some really exquisitely executed modernist cuisine - the smoked pigeon carpaccio was spectacular - but our budget only allowed for it because we were staying with family and thus not paying for a hotel for our trip. This is the anti-Al Atlas. Dinner for 2 was 40x the price, and while I'm sure the ingredients, facilities, and staff were also on the order of 40x the price of Al Atlas, I'm not sure I enjoyed dinner there 40x more. Still, if money's not a consideration it's worth going.
* Bar Velodromo is open 24x7x365.
We went on Christmas day for lunch. It's not a bargain during normal times, but the oysters were lovely, likewise the beef with chimichurri, and "el siscento BCN" with eggplant and roasted peppers. Mostly what's great about this place is the ability to eat well at any time, any day of the year.
* Bar Nou for pa amb tomaquet.
Another random on-foot find, this place opened for business just before we left town. Stylish, minimalist interior design. This place specializes in bread with tomato, the standard catalan accompaniment to any meal (though I can make it a meal in itself.) We went for breakfast on our way out of town - they are open 8am - midnight. I wish we had had time to try more here, but the toast with lemon, sugar and olive oil was a revelation. I'm still trying to replicate it at home.