Cool, unique things / places in Tokyo?

Hi all,

I'm going to Japan on holiday in March, and at the moment I'm putting together a travel itinerary. Half the time I plan on travelling, but the other half I plan on spending in Tokyo.

I lived in Tokyo for a year and so have taken part in many customs and visited many of the traditional tourist sites (the Tower, Odaiba, the Kabuki in Ginza, tea ceremony, ikebana). However, I'm sure there is plenty that I've yet to experience - tons of bars I've heard about, maid cafes...

So, does anyone have any suggestions for off-the-wall stuff to do in Tokyo - or Japan in general?

...difficult question!
But I'd like to hear some answers too ^^

When I was in Tokyo, I've been to St. Mary's Cathedrale. Unfortunately I took the wrong entrance, at that time I could only read the signs for iriguchi, and thought I was right. Though I was wondering why the stairs led downwards and it rather looked like the basement, I went on and finally opened the door.
There it was, the mortuary and fifty heads turning round!
Though it was kind of embarrassing, it sure was a unique thing... ^^

To continue with the dead, I went to Higashi Otani Mausoleum in Kyoto. I know you shouldn't take photos of graveyards in Japan, but the view is fantastic! You can look it up at Google Earth. The contrast of the graves in the front, and the city in the back is really great.

I once saw a zeppelin over Toyko. Wish I had the money to do the ride...but perhaps there are some hot-air balloon rides available?

Well, what I certainly want to experience on my next trip is a love hotel. Though I guess you shouldn't be single therefore ;)

Can't think of anything else at the moment, but I'd like to read some further answers!