Since there's a general manga thread for this, and I think the untranslated Japanese volumes would be a shorter list for most people, I decided to make this thread.
What Volumes of Japanese Manga do you own?
These are mine:
Dragonball: 1-5 (Tankoubans)
Dragon Quest 4 and 1 (Special 1 Volume Manga)
Dragon Quest: Emblem of Roto: 1-20
Dragon Quest: Emblem of Roto, Those that Inherit the Emblem: 1
Dragon Quest: Dai no Daibouken: 1-37 (Complete)
Dragon Quest Monsters Plus: 2
One Piece: 1-38 (Complete to date)
One Piece: Movie 4 manga: 1-2 (Complete)
One Piece: Movie 5 manga: 1-2 (Complete)
Ranma 1/2: 1
There are a few others, but that's all I can think of at the moment.