Not really alot to say, other than that Berserk is the darkest and most twisted thing I've ever read, and it's amazing despite and because of that.
Vinland Saga has a similar art style to Berserk, but come on, it's about freaking VIKINGS. That's reason enough to read it right there.
Vagabond is a samurai manga, but oh-so-much better then your generic samurai manga. Read it too, once you're done with Berserk and Vinland Saga, anyway.