Best Cheap Lunch in San Francisco?

I used to tell myself back in 1980 (when I worked in downtown Nevada City for Crittenden Publishing) that what what my town needed more than anything was a good $3.00 lunch. Whudda guessed I'd find it 27 years later in San Francisco?

Zapata's at the northwest corner of 18th and Collingwood is a modest taqueria (a redundancy, I know, but a useful one) offering the usual fare, which no one needs me to list. Very rarely, the cook tapes a handwritten special on the spit guard separating the mostly illegal, no doubt, immigrant servers from their customers. This isn't the world's best taqueria, though I'd rate it above average. A weakness: its slim selection of salsas and no cut limes.

A major strength: The fish taco. These are much more generous and flavorful than the standard San Francisco specimen. Can't tell you what it is, but the main ingredient, cooked to order right in front of you on the always-sizzling griddle, is white, fresh, firm-fleshed but somewhat flaky, and remarkably flavorful. Your choice, natch, of black, pinto, or refried beans and either mild or spicy salsa. You can also choose between regular and super, which adds -- unnecessarily in my opinion -- guacamole, sour cream, and maybe cheese. I always order black, spicy, reg. The unusual and impressively successful ingredient Zapata adds to its signature fish taco is fresh mushrooms, a lot of them, griddled along with the fish.

A single regular fish taco comes with a little rectangular paper box of fresh corn chips. You can load up with roasted tomato salsa, a raw radish or two, and easily call this lunch. Or at least I can. With free water, the midday meal comes in at $3.10.

I'm always satisfied, never tempted to have more, and go back regularly, as does Dan. There's no reason for this to be a secret. Tell everybody!

Your turn: Any other nominations for San Francisco's best cheap lunch?