Krieg/Krieg's Buzz Axe

Krieg's Buzz Axe receive various visual upgrades depending on skill selection.

Basic Axe
His classic Buzz Axe, with no visual upgrades.

Empty the Rage
Adds a pointed metallic cap the the base of the axe's handle.

Strip the Flesh
Adds a pointed guard just below the head of the axe.

Release the Beast
Attaches a grenade to the back end of the axe and bigger blades on top of the default blade.

Buzz Axe Bombardier
Adds sticks of lit dynamite to the side of the axe.

Fire Fiend
Grants a bright orange accent along the sharp edges of the axe.

Everything
Mix all of the Previous upgrades.

Source
http://forums.gearboxsoftware.com/showthread.php?t=290256