Akihabara is probably one of the coolest districts in Tokyo and Japan overall. It's very easy to access it by a JR line train via the a really big station and being hard not to notice the big sign pointing to the Electric town.
There is just no way one could get bored in Akihabara. The place is full of shops that sell a lot of stuff from electric appliances (really affordable and good quality), hi-tech devices such as enormous tablets, anime and manga merchandise (like manga books, figurines, DVDs and CD soundtracks) and a lot of video games and consoles (both old and new). If, like myself, you like PS2 era video games you will somehow feel right at home because the said console is still for sale and it is possible to find some cheap but very rare games.
Akihabara is also the perfect place to try out a few of the many themed cafes available. I visited Maidreamin' Nº1 (featured on WORLD ORDER's "Have a Nice Day") and it was super fun. The maids are adorable and very nice. It is a bit pricey, though, but it is worth it to try it once.
Also, if you like photography, it's possible to take some cool shots of people cosplaying and also of street performers. Although, the very tall and covered in spectacular ads the buildings are also perfect to photograph.