I think one of the best things about San Francisco is the food and drink. Haven't seen too much of that here in this thread so that's my contribution:
FOOD
* Kin Khao – An amazing Thai restaurant that’s in the Parc 55 hotel in Union Square. Good for lunch or dinner, you probably need to make a reservation. Everything is good but I recommend the “pretty spicy wings” and the “Yaowaraj Noodle”
http://kinkhao.com/
* Molinari Delicatessen – One of the best sandwich places I’ve ever been to. You get to choose your piece of bread from their bakery area and then they make your sandwich with that bread at the deli.
http://www.molinarisalame.com/
* Tony’s Pizza Napoletana – They have 11 different pizza ovens (the best one I've tried there is NY style). Rated one of the top 5 pizza places in the entire US on a handful of lists.
http://tonyspizzanapoletana.com/
* Tommasso’s – They don’t take reservations so it’s best to go shortly after they open (5:00 Tue-Sat or 4:00 Sundays; Closed Mondays). Really good southern Italian style place with a big table in the middle and a few booths on either side. The pizza here is really good as well (I usually get it as an appetizer for the table).
http://www.tommasos.com/
* Scoma’s – Really good seafood restaurant near Fisherman’s Wharf in an amazing location right on the water. The Cioppino (a San Francisco invention which is a ton of great seafood in a tomato broth) and Lobster Bisque are two things I’ve gotten here and loved.
http://scomas.com/
* Boudin – A bit touristy but I always like this spot at Fisherman’s Wharf. Clam Chowder in a bread bowl is the best here because they bake the bread right there. Grilled cheese is amazing there (with bacon!). Good quick lunch spot.
https://boudinbakery.com/boudin-at-the-wharf/
* Anchor Oyster Bar – Amazing seafood and a great clam chowder. It’s in the Castro area so it’s a pretty fun area of town to even just go see. When I go here, I'll write my name on a list then head to one of the great bars in the area like Harvey's then go back before my expected time.
http://www.anchoroysterbar.com/
DRINK
* Local Edition – Awesome cocktail bar that used to be an old newsroom. One of my favourite things to do here is just tell the bartender to make whatever he feels like for me (he’ll ask if I want it to be sweeter, boozier, what main alcohol I want in it, etc.). It also often has live music.
http://localeditionsf.com/
* Bourbon & Branch – Speakeasy bar where you need to make reservations to get a password. Or if you don’t want to make resos you can go around the corner to a side door and let them know that the password is “Books.” It’s a small room that looks like a library.
http://www.bourbonandbranch.com/
* Jones – A fun place with a heated outdoor patio. Good food and drinks. Bar-type food.
http://620-jones.com/
* Smuggler’s Cove – Pirate-themed tiki bar named one of the top bars in the US.
http://www.smugglerscovesf.com/