5 Things you MUST do in Japan

What are in your opinion the 5 things that one should definetly do during a trip to Japan. From eating sushi, taking an onsen or watching a sumo game, to climbing mount fuji and etc.

I'll write mine here later..

Do you mean for first time visitors?

For those going to Japan for a first time visit, I'd say the following:

-Visit Meiji Shingu Shrine.

-Visit Shibuya/Harajuku/Aoyama on a Sunday.

-Visit/Shop "Electric Town" Akihabahara.

-Climb/Visit Mt. Fuji in the early morning.

-Go to the Tokyo Tower at night when the tower is lit.

-Walk along Nakamise Dori to Sensoji Temple

-Ride the Shinkansen to Hakone, Atami, Nikko or Kinugawa and stay at one of the traditional onsens.

For those re-visiting Japan:

-Visit cultural landmarks in Kyoto, Osaka and Nagoya areas

-Go snowboarding/sking in Hokkaido

-Go scuba diving in Okinawa

-Visit Tokyo Disneyland

-Go to one (or all) of the big four festivals of Japan - Aikawa Kinzan Matsuri (July 25-27); Ryotsu Tanabata Matsuri (Aug 6-8), Sawata Shishi-Ga-Jo Matsuri (Aust 10-11) and the Ogi Minato Matsuri (Aug 28-3).

-Visit Ueno Park during the Cherry Blossom season (April).

In a general sense:

try the food,
see the sights,
talk to locals,
go for a hike/do some other physical activities,
go to a festival.

I'll get into specifics later, if I can remember.

Stay at an onsen.
Eat at a kaitenzushi or ramen restaurant.
Go to one of the A-bomb memorial museums.
Ride the shinkansen and compare to a local train (especially in the countryside).
Attend a major festival.

Totally location dependent.

Try a ramen cart. Kaiten Sushi is definately a must for first timers.
Visit a shrine
Eat Yakiniku,
Explore the "downtown" area
onsen (still haven't been to one)
Visit a Park.