Myrna's list is great. I'd like to add drinks: my boyfriend loves ramune, you have to at least try calpis (the Japanese version of a sports drink) and I always get bottled oolong. It's the type they sold in vending machines in Japan when I lived there and it's very nostalgic for me.

The produce section at Uwajimaya is awesome. They have everything from nopal to daikon to some of the coolest fruits you'll see. In the fall you can get fuyu persimmons and eat them like an apple. I always get baby bok choy here.

One of my favorite summer foods is soba, and I buy tsuyu to dip the cold noodles in. With sesame seeds and green onions.

I should also point out that a great chocolate snack are the Lotte koalas. The little hollow ones filled with chocolate.

Cream puffs are a convenience store staple in Japan, so even the packaged ones are yummy! Also, anything with azuki beans. Especially manju. And everyone who cooks white rice should have furikake to sprinkle on it; I use this in onigiri as well.

I like the Hawaiian takuan. The frozen veggie mixes of carrots and burdock roots as well as the nishime vegetables are nice and convenient. The sea vegetables totally rock. In general they have a top notch produce section with great selections of mushrooms and hard to find fruits. I also love the sake selections. Onokoroshi is my favorite.

Then there are the packages of pork bungs. Nothing says love like pig asshole casserole.

Koji made by Cold Mountain (described on the package as rice kernels covered with a fragrant white bloom of Aspergillus oryzae mold) -- you'll need it for making your homebrew sake!

It's also a very cheap source of white tea. I recommend the big 200g boxes of shou mei white tea by Foojoy ("longevity eyebrow" tea -- sweet, toasty flavor).

In the produce section, it's the only place I know of to buy myōga (sometimes called "Japanese ginger" but with a flavor of its own) in season.

Shitaki mushrooms are cheap and plentiful and they have the best pork in town. I also love Hawaiian Host Caramacs and the yellow-boxed Carmels by the checkout.

Mochi! Ice cream in rice paste. So weird and delicious!

Or black sesame ice cream bars. Nothing is cooler than delicious black ice cream.

Asian crunchy snacks are great. Calbee Shrimp Chips. Calbee Green Pea Crisps. (They're not the same as the ones at Trader Joes; the ones in Asian groceries have powdered fish in them and taste much better.) Fried rice crackers.

Pretty much any snack by Calbee is worth trying. The BBQ corn snacks don't taste like any kind of BBQ I've ever had, but have a nice savory soy-sauce and corn flavor unlike any American snack.

Hum bao... Delicious, and they have pretty much every kind imaginable! Plus there is refrigerated or frozen, which is nice.

I also love that they have Aloe Juice, which I guess is not so rare anymore, but it is pretty crazy and amazing.

The last thing that shocked me was Milo! They unfortunately only have the energy drink version, last I looked, but I would be so amazed and pleased if they had the Milo granules like what is so popular in Australia. I miss that.

Oh god, the ginger cookies. I haven't gotten any in years, but those things used to be a serious addiction for me. They have the texture of fortune cookies, but they're ginger, not that nasty almond extract crap.

frozen pork bunz!! sweet, easy to re heat, and I actually cried once when they ran out. Hum Bao!

Oh, where to begin... Miko Brand Dashi Miso - miso with dashi already mixed in for instant kick ass miso soup. Choco-gummy,(Gummy-choco?) little chocolate coated balls of artificial greatness. Korean kimchee potstickers. More types of kimchee than you can shake a green tea sponge cake roll at. Everyburger, quite possibly the silliest candy EVER. Good, cheap sake in 1.8 liter milk cartons. Smoked squid salad. Of course, ramune and Hello Boss! canned coffee. I could go on...

I love the pre-fried tofu cubes. You can marinate them if you like or just toss 'em in with a stir fry or a curry. They have that crisp/chewy outside that I love on fried tofu but haven't been able to perfect on my own.

Absolute favorite: Jackfruit Chips! These little, freeze-dried nuggets of jackfruit goodness make my snack day every time. And since the're a fruit (or at least fruit based), I can pretend their healthy. You can find them around the produce section.

The frozen ramen at Uwajimaya is approximately 1,000 times better than dried grocery-store ramen. Just be sure to follow the directions (separate boiling water for the broth and the noodle-cooking) or it comes out weird. The tea selection is pretty great... also love the wasabi peas (fun to put in your roll-your-own sushi!) and everything else y'all have mentioned too.

And P.S.: A great sushi chef just told me that Maruta Shoten in Georgetown is like a way smaller, way cheaper Uwajimaya. WANT TO GO NOW!

sausage casings, mugi cha (almost soothes a postum craving, RIP postum), guchjang for making your own kimchi stew just right, cute non-plastic food storage bowls, and tiny, weird STICKERS!!!

The "Mushroom of the Mountain" cookies are absolutely amazing. 

The coated peanuts are also great. They have a smooth, crispy shell, usually flavored with BBQ or some kind of cheese powder.

Anything kind of dumpling or filled bun is good in my book also.

Not directly answering the question but related - most of the stuff everyone has listed is also available for slightly cheaper prices at Viet Wah on 12th & Jackson

The mini-cans of cold cinnamon beverage. Not soda, maybe a punch? Not sure what to call it but it is delicious and cinnamontastic.

Great fruit and veg at amazing prices. Meats I either can't find anywhere else (pork ground for sausage making), or is half the price at Uwaj - ducks. A profusion of fresh, well-priced oysters and other live seafood.

But the item that other people enjoy that I bought at Uwaj? The reusible Dragon bag. Use them for all my shopping, and I've had people try to steal them. Seriously! Get your own, they're only $5.00!

charumera tonkotsu ramen, bonito furikake, zippy's chili (frozen), japanese candy

Every once in a while they'll get Fanta from Japan. I'm actually in Japan right now so I'm getting my fix of crazy Fanta flavors, but it's always fun to stop in and see something back in Seattle that I can't get anywhere else.

Two things I absolutely cannot find elsewhere:

1) A sushi-grade fish selection beyond just Atlantic salmon (for my favorite kind of "roll-your-own").

2) soy paper: for those of us who aren't huge nori fans, this is the only place in town outside of a sushi joint I can find the soy paper substitute.

Sapporo.

Japanese nylon washcloths. Great for back scrubbing.

Sake sets where the little glass vase has a bubble inward on the side for chunks of ice, to keep the sake cold while not watering it down.

Sake, both imported and domestic.

The green apple gummies!

Seriously these are the best gummies anywhere, so delicious!

When I was away, I used to have my sister who lives in Seattle head over to Uwaj (we're on a nickname basis, me and Uwajimaya) and pick up a few packs to mail to me.

They cannot be tamed.