618 Shrader St.
1512 Haight Street
If you can't afford a ticket to Tokyo, San Francisco's not a bad second choice. There's an entire neighborhood of Japanese expats and immigrants, sushi restaurants on every block, and within earshot of each other, two stores specializing in the more rarefied artifacts of Japanese-style mass culture - the consumerism-as-art-form urge to collect, the forced scarcity of deliberately-limited editions of things like keychains, and the fine line between street and gallery art (if you're still convinced graffiti is never capable of being more than vandalism, take a pass). This is the stuff you buy when you're a well-paid adult who grew up on Sanrio or an art director who still owns a skateboard. The rest of us are free to browse to our hearts' content. Both Kid Robot and Giant Robot have exactly three stores each - in NY, SF, and LA - and are about as hip as those addresses would lead you to believe. That cool co-worker who listens to all the bands and has interesting eyeglasses? He may have gotten a lot of his cute-but-sometimes-creepy cubicle decorations or that copy of I Am Plastic from one of these stores.
Kid Robot is the smaller, more esoteric shop, stocking primarily vinyl sculpture (the naive will call them toys). Most of the stock is custom works in limited edition, sold exclusively by Kid Robot, in prices starting at around five dollars. Kid Robot commissions clothing, sculptures, the occasional piece of jewelry, de rigeur cell-phone straps, and art prints and posters. Rarer pieces can cost several hundred dollars, and are protected from your filthy fingers in locked glass cases. These are serious toys, people!
Giant Robot is a little more easygoing (it doesn't feel like an art gallery), a little more book-heavy (it's the retail face of a long-standing magazine about Asian pop culture) and, most importantly, they sell t-shirts at lower prices than Kid Robot. They also tend to focus on a slightly different group of artists than Kid Robot, making the two stores less direct competitors than symbiotic partners.
Both are big fans of my favorite toy designer Mori Chack - his Gloomy Bear character is featured on the cover of the current issue of Giant Robot, and in vinyl figures at Kid Robot (with and without bloody claws and muzzle). You'll see a few of the same products at both stores, but not that many overall, and both are worth visiting, especially because they're so close to each other.