I'd just want to brag that I'm in Tokyo now and man, is it a wonderland. I bought maybe 45 games so far, mainly at Chiba Kanteidan, Super Potato and Friends. No real rare games so far (Guevara was a bit pricey at 5000Y though) but going back another day for Spartan X2 and maybe others.
Gimmick is 42800Y though so probably not that one unless there's a cart-only one for less.
Are you there alone? While being there I recommend eating at lots of different restaurants and hitting the karaoke and game center. Game centers aren't what they used to be but compared to the current arcade situation in Sweden...
Food to try if you have time:
Ramen (Chinese noodlesoup)
Soba (Japanese noodlesoup)
Udon (Japanese noodlesoup)
Yakisoba (fried Chinese noodle dish)
Gyoza (often included with ramen sets)
Sushi (not just avocado and salmon like in Stockholm, many more types)
Yakiniku
Yakitori (tori means bird but it actually often includes other kinds of meat as well)
Karaage
Tenpura
Unagi (a bit expensive but not as expensive as in Europe)
Okonomiyaki
Karee (Japanese curry. If you like spicy you can usually order really spicy curry)
Drinks to try:
Beer
Shouchuu
Umeshu
If you are with friends you can go all out on an izakaya with tabehoudai (all you can eat) and nomihoudai (all you can drink).
Also now is a perfect time for viewing autumn leaves (紅葉 kouyou) if you can ask someone where to see it.
Have fun! Be sure to check out Trader (2nd floor). They've got a great selection of Famicom titles at reasonable prices.
Also, at least a few different Book-Off (and Super Bazzar) places have a ton of common titles for FC and SFC marked down to 108 yen each. The one in Tsunashima's the best example.
If you need directions or anything, send me a message. I work in Akiba.
I would highly recommend avoid food from unknown sources(yup restaurants), because most Tokyo supplies are around Fukushima, Chiba and Ibaragi area. If you are ok with some extra minerals, which you can get, go ahead. Same about fish.
And don't waste your money on japanese "beer"
Otherwise all good.
There's plenty of gre...goo...dece....
Yeah, maybe don't spend too much money on Japanese beer. Not a great cost/value ratio. Unless you do the aforementioned nomihodai. In which case, hey, go nuts! :)