Cowboy Bebop. Hands down, end of story. I hardly watch any anime to begin with but have seen a few. Dragon Ball Z was sort of a silly, fun guilty pleasure of mine. Outlaw Star was watchable when I was bored, but definitely had its defects. I also thought Ghost in the Shell: SAC was fairly decent. But nothing, and I mean absolutely *nothing* beats Bebop. The characters were believable as actual human beings that people could relate to, it had a great 'used future' look to it, and most importantly had an outstanding story that didn't rely on stupid gimmicks during its 26 episode (plus a movie) run. Don't even get me started on the awesome soundtrack.