I started this list on the running on empty list on yahoo groups, but will continue it here, since I ran out of time for posting there. If you want to read the rest, you'll have to subscribe. It will likely be good for you ;-). Obviously, this is pegged to my climate (upstate NY) and my garden (clayey and rocky, with lots of chickens in it) so YMMV.
Sweet potatoes - mostly, I don't have to buy slips any more, since my original Georgia Jets and Porto Ricos usually last long enough to make more, but if I do, those are the two to get. Store sweet potatoes don't taste nearly as good as mine, and if I can grow them, pretty much anyone south of Montreal can. They store all year for me, and are an essential staple.
Peppers - I posted about peppers on the other list, but I wanted to ask here also - anyone know a good OP korean hot pepper? I can't live without my spicy korean noodles and kimchi, which require peppers. The only one I've found is a hybrid from Evergreen.
Also, anyone have a favorite habanero for the north? I like 'em fiery.
Eggplant - I love eggplant, and for some incomprehensible reason they grow really well in my cold, wet garden. Don't ask me. Ichiban has been most reliable for me, but is a hybrid. Pingtung long does ok - I had one strain that did much better, but I can't remember where I get it. Rosa Bianca didn't do well last year, but did the year before. And the Turkish Orange ones always go bananas, and no one but me likes them (kind of bitter). I find eggplant keeps best dried.
Huckleberries are amazing, and I don't know why everyone doesn't grow them. They grow just like tomatoes, are incredibly prolific, and you can have berries in one season. What's not to love? I get mine from Baker Creek, but I might try seed saver's wonderberry later.
Celeries and the like: The only celeriac I've ever tried is large Prague. Love it. The leaves make a good celery in soup. I mostly don't grow celery any more - too much work, too heavy a feeder, takes up a lot of space all season long, and what do you get? Celery. I do grow zwolsche krul cutting celery and lovage, both of which dried give that flavor to soups without all the bother.
Daylilies - Cold climate permaculturist's dreams. The petals are the best tasting flowers I've ever eaten - sweet and crisp. Mine bloom for a month or more. The buds are great dried in soup. The root is tasty, and the shoots are great in the early spring when not much is growing. And they are so pretty. Plant a lot.
Strawberries - for years I've been looking for "Fairfax" strawberries, and can't find them. Laura Simon, The Nearings, Ruth Stout, Gene Logsdon - every one of them say they are the best tasting strawberry out there, but they seem to be gone. Anyone know where to find them? I grow "Sparkle" their step-child, but it isn't as tasty or, I gather, as disease resistant. People are insane - they have a perfect strawberry, and they throw it away for something new and sparkly. May whoever is responsible have to eat supermarket strawberries for a long, hot, eternity, while the real things send their perfume from just out of reach. (Ok, maybe that's a little excessive. But I want that strawberry.)
Arugula - I'm excited to try seed savers astro, which supposedly has bigger leaves - I could eat arugula by the vat every day, and I can usually manage to keep it going from april to november, so I do ok that way. Ordinarily, I grow whatever, plus the sylvetta, which is a little pointier and, I think, a little spicier.
Chard - Customers like the five color silverbeet stuff - Seed savers has a great strain. But I admit, my two favorites are "Argentata" and "Fordhook" Chard is a wonderful plant and no one sings its praises enough. It will grow all through the hot of the summer and the cold of most of the winter. It is delicious, simple, nutritious and pretty. You can eat the ribs like celery, or put them in soup and dye it pink. As a baby green it makes one heck of a salad. And the more you pick it, the more there is.
Broccoli. I'm still working on a favorite OP broccoli - except that I really like "Romanesco", and Eric likes it because it is a fractal (and tastes good). Rosalind (Territorial) has done well for me, as has Purple Sprouting (I can't remember - maybe Baker Creek?). But I've been using hybrids for early crops, and they are more reliable. I've got to work on that. It isn't really a storage crop, despite its nutritional value, so it isn't a huge priority.
Squash - I love squash. I can't live without hubbards. I know they make small ones, but it seems so sad to grow a 5 lb squash when you can grow a 30lb one, and the chickens and ducks so love baked squash that if we actually leave some, they will. Plus you can put it in soup, bread, pasta... Butternuts are a main crop, and plain old Waltham is a proven winner. I love Futsu, which really does taste nutty - kind of of like beech nuts, and has a cool smell. Oh, and I love zucchini - all zucchini. That makes me weird, I know.
Borage - the blossoms really do taste like cucumber, are amazingly pretty, and fun. Plus, it will show up forever. Add salad burnet, and if your cuke crop fails (as mine mostly has two years in a row) you are set for that cuke taste. Tough to make pickles of, though ;-P.
Cucumbers and I have a hostile relationship - I've had dreadful crops the last few years. We are down to 1 jar of pickles - sigh. I love poona kheera, delicatesse, and national pickling, but they don't love my garden.
I'm sure I should post more, but I'm tired and lazy. My husband has promised me thai beef salad if I'll wind the skein of yarn for his next project, and I am a whore for anything in lime juice and fish sauce dressing. Sorry.