Interesting topic. Berserk characters are so well developed and fleshed out that it is nearly impossible to describe each one of them in one word. Therefore, I'll only use words that describe what I like or dislike the most about them.
Guts: Integrity - That's one thing I always admired about Guts. Whatever faults he has, Guts is an honest man. There is a strength of character in him that sets him apart from almost anyone in the series. I'm pretty sure if he had been in Griffith's place during the Eclipse, he'd have told the God Hand where to shove it.
Puck: Goodness - I would have picked Mischief, but I thought I'd mention a quality of serious
Puck is one of the few characters who have always been good. He served as Guts moral compass, and helped preserve his humanity, among other things. The series would have been poorer had Miura never conceived this character.
Casca: Loyalty - Casca's one person that, when her loyalty's earned, would never let anyone down.
Farnese: Sincerity - Her wish to learn more about magic, her wish to be 'useful' to the group even though she was, and so on have always been sincere. That is one of Farnese's most admirable qualities.
Serpico: Cunning - I've always been impressed by Serpico's displays of brilliance throughout the series. Ever since he threw that piece of wood on Guts' legs as he was about to get Farnese, I knew Serpico would be someone to watch out for.
Schierke: Resourcefulness - Really what can this girl not do? Ever since she joined up with Guts' group, she has been, more or less, the brains behind the operation, having a solution to many of the problems they encountered. It is all the more impressive considering her age.
Isidro: Resourcefulness - Again, but of another kind. The situations he adapted to and got himself out of prove this.
Roderick: Competence - I initially misjudged this character at his introduction, dismissing him as no more than another spoiled noble. But he has time and again demonstrated his competence, most notably as a captain of a warship.
Rickert: Engineer - As an engineering graduate, I had to pick that one...on a more serious note, I'd say Bravery, due to that scene with Griffith on the bridge of separation. Other than that, Creativity.
Judeau: Perception - Really, hardly anything got past this guy. He's one dude I wouldn't want to be around if I were up to something.
Godo: Wisdom - Aside from being a badass blacksmith, Godo offered some of the most memorable lines in the series. That speech alone when he called Guts out on his BS established him as one of the wisest characters in the series.
Dragon Slayer: Symbol - Dragonslayer's size and impracticality is more than just a 'badass factor' for Guts. Those two aspects make the sword a character itself, representing Guts' almost insurmountable odds and the great struggle he puts up.
There are so many other characters one could talk about, but those will do for now.
