Arcade "Oslo Game" - Shinjuku, Tokyo

Contender for smallest arcade in Japan.

Just a few cabs and a bunch of UFO catchers but still worth a mention. Deep in the heart of Kabukicho there are a few of these places tony arcades scattered around, essentially pandering to the Hosts and Hostesses working in bars around the local area.

Ground floor has a few throw away games, but good fun if you're wantin to up your Mario kart skills. Mainly UFO catchers..
Second floor - darts, with just a few Gundam cabs.

Oslo itself is an independent arcade chain spread around a few places in Tokyo (Tachikawa's being the biggest joint).

GAO - Shinjuku, Kabukicho

5 years fumbling aroun Tokyo completely missed this one.

Tucked away on a side street in Kabukicho, chances are most visitors will miss this place simply trying to avoid sex touts in the area. Nevertheless, definitely worth searching out.

Tekken, Street Fighter and Taiko are pretty much the only things going on gamewise, but overwhelmingly you're going to want to check this place out just for the competition. Located in the heart of Kabukicho means that scouts, hosts and hostesses all come here during lunch breaks to game - and they are all good. Real good. Personally it's the most authentic of gaming experiences to go head to head with a dude in a tuxedo playing claw on Street Fighter. Or an Anna/Nina player in an evening gown.

Definitely worth supporting - 4 songs on Taiko for 100¥ is phenomenally good value for money.
DD

Retailer "TSUTAYA" - Shinjuku, Tokyo

One hell of a huge ass gaming music collection!

Although claiming the largest porn selection in Tokyo, their gaming section ain't nothing to be scoffed at. You name it, everything from Street Fighter to Final Fantasy, obscure remixes to the Pokemon movie, this place is gonna have something to make commutes just a little more bearable.

TSUTAYA's prices are pretty ruthless but a lot of these tracks are completely off the radar.. Definitely worth a visit.

新宿ＴＳＵＴＡＹＡ
3-26-14 Shinjuku, Tokyo 160-0022
http://goo.gl/maps/ustrn

Retailer "Bicqlo" - Shinjuku

Japan's first "Bic Camera", "Uniqlo" crossover is the latest in a sea of big brand collaborations, this time bringing electronics and fashion to one mega store. Access from Shinjuku and Shinjuku Sanchome stations through the underpass make it unmissable.

Although not having the breadth of selection the usual "Bic Camera" would usually offer, "Bicqlo" has a bunch of promotions and offers exclusive to this particular branch.

Exclusive free gifts on pre ordered goods.
Periodical promotions and discounts (combined with their point system makes for good savings).
Promotional life sized models during DVD or major game releases (including Dark Souls, Pokemon, Gundam, IronMan, Spider-Man etc).

ビックロ
Japan
http://goo.gl/maps/3tjkW

Trader "BookOff" - Shinjuku, EastSide

A whole buncha reasons to be there.

BookOff joints vary from place to place, supplying, as guessed, books, but also a whole slew of CDs, DVDs, magazines and game soft/hardware.

This particular place in Shinjuku is credited as one of the largest in Japan - their gaming section speaking for itself. Dealing in just about anything that can be spun for a buck means they also accept old school gaming stuff. Prices range from insanely cheap to reasonable and always have a diamond or two to be found.

A retro gamers paradiso, definitely worth going out of your way to check once a week.

Sellers beware, you're gonna get a bum deal droppin your stuff here - Akiba/Ebay all the way.