Whenever I find myself in New York City, one of my favorite places to visit is always Kinokuniya Books on the West Side of Bryant Park (1073 Avenue of the Americas). Rather than try to describe to you why I love this store, I offer this:
The Kinokuniya gel/ballpoint display. I'm not sure there's another B&M retail store that stocks this kind of variety in the United States (with the possible exception of Maido Stationery in San Francisco, which I understand to be affiliated with Kinokuniya).
This display is just one of their pen/pencil/stationery racks. In this picture, across the top, from left to right, are displays of jetstreams/acroballs, Pilot Hi-Tec-Cs, Signo DXs, and Sarasa Clips. Mixed in among them you will find Energels, Sliccis, Frixions, the entire range of Pilot Varsity disposable fountain pens, and various other gems.
While I was in the store, they had just received a massive shipment from Japan and were in the process of restocking their inventory. The store itself is pretty small, so I couldn't get in a position to take pictures of the pencil display (which is just as large as the pen display) featuring pretty much any kind of mechanical pencil, japanese woodcase pencil, erasers, and leads you would want to get your hands on.
Under glass, in a display case, Kinokuniya has a more-than-respectable selection of Pilot and Sailor fountain pens, as well more expensive gel pens and multipens such as the Pilot Cavalier Hi-Tec-C and the Zebra Sharbo DX. I have bought Sailor ink here before, and I believe they also carry Iroshizuku, but I didn't ask because I wasn't in the market for ink this trip. (All fountain pen ink is kept behind the counter and not on display.)
Kinokuniya also devotes the entire back wall to notebooks and paper. Again, it was a bit of a mess with employees pulling things down and rearranging the display racks, so no pictures this time, but they have notebooks from Figurare, Apica, Midori, Rhodia, Campus, and other Japanese brands I had never seen before. If you are looking for refills for your Midori Traveller's notebook (or to pick one up), they stock the full range of refills and accessories in both sizes.
My purchases this trip:
I picked up a couple of unbranded pocket notebooks, a Pilot Hi-Tec-C Slim Knock, a .38mm Jetstream in blue, a .25 mm Pentel Slicci in black, and a .38mm Zebra Sarasa Clip in blue black.
Kinokuniya is a great pen store. They also carry both Japanese and English language books and periodicals, Japanese stationery items such as Washi tape, paper clips, and art supplies, as well as a full range of calendars and planners. (No Hobonichi Techo, I asked.) If you live in the NYC area, or are just passing through, I highly recommend stopping in and picking something up. After Art Brown closed down last year, I always make it a point to support these stores and do my part to keep them around.
Here is a link to their website, although they don't sell stationery online, to my knowledge.