there is no "best" build. it depends on your playstyle. if you like melee, make use of his berserk action skill alot and skill him focused on iimproving his skill. if you like explosive weapons and/or rocketlaunchers, go for the blaster master tree. whatever you like is the best build.
As said above, it totally depends on your playstyle... however, check the builds section of the wikia for more info. Personally, I use a melee specced brick (SUPER PUNCH OUT) http://borderlands.wikia.com/wiki/Character_build