I'm a grand old Trigun and Trigun Maximum fan. I recently completed my collection (the final volume was just realised in English). Amazing story, but I did have some problems with it (mostly, some of the really endless fight scenes and the way the mangaka drew them, it was difficult to tell what was going on for much of them). I really wished Nightow would have stuck with "more philosophy less badass macho fighting" - not that the badass macho fighting was bad, it just would have bee nicer for me if it came in smaller doses, interspersed with more of the philosophical stuff that really *makes* Trigun.
I got to be a fan because of the anime, but the manga has its benefits, - really cool characters such as Livio the Doublefang. Livio was just plain awesome.
Anyway, I have the first two volumes of the original Trigun, then all 14 volumes of Trigun Maximum (same series, name chaned because of a Japanese publishing rights issue). I even have a few volumes in Japanese, though I do not know how to read Japanese, and one of these volumes has been autographed by mangaka Nightow himself.
I have a few other mangas floating around.... from where I'm setting, looking at my bookshelf, I see one of the volumes of Osamu Tezuka's "Phoenix" that I have. I only have the first two volumes of that... I believe it's something like 12 or 14 volumes, all seperate stories, and the series was never finished because Tezuka died before he could... I have the first three volumes of his "Adolf" series (great if you like Historical drama)... I have the whole first series of "Petshop of Horrors"...
I have quite a bit of manga, but my only truly complete series is Trigun/Trigun Maximum. When I was low on money, my manga money went to that because I'm a dedicated fan.