A fan of roller coasters? You MUST go to Fuji-Q!
Although I've only been there once, it was an excellent enough amusement park to say that Fuji-Q Highland is my favorite amusement park in the world. This is a great amusement park for people who like heights and fast roller coasters. Although it can take a long time to trvel to Fuji-Q and can close early at 5pm, the rides definitely outweigh the disadvantages. My favorite ride is "Eejyanaika;" watch this video to see what this video is like http://www.youtube.com/watch?feature=player_embedded&v=kCpdkIcqFUM. There is a new ride, which is known to be the ride with the steepest drop, http://www.youtube.com/watch?feature=player_embedded&v=M9QOaAY8g1U#at=95. I look forward to going again soon to ride this roller coaster!
This is the website for Fuji-Q Highland in English: http://www.fujiq.jp/en/index.html
I definite must-go place in Japan if you're a fan of roller coasters!