death note...kinda...bored me a little bit to be honest. The manga is much better.
Plus, of course, you should start reading the manga (berserk)
you can read it for free on this website:
http://manga.animea.net/
The berserk anime ends at about halfway through the manga and skips a bunch of great content.
as far as anime is concerned;
Fist of the North star - http://en.wikipedia.org/wiki/Fist_of_the_North_Star
~100 episodes and a (i think) a couple movies, but maybe just one. The main character is very similar to Guts in that he's a lone wanderer and violent and unstoppable.
Ninja Scroll - http://en.wikipedia.org/wiki/Ninja_scroll
Another lone wanderer kind of movie, this time set in feudal Japan. The main character is superbly skilled in swordplay and fights 7 or so demons each with unique abilities. He is joined by a female ninja and a mystic. very bloody and serious.
there's also this robot anime that is partially done with CG that I cannot remember the name of at the moment, but I will post it when I get home and look on my pc.
