EXETER:
Exeter comes to mind when considering high powered guns. Despite its 
simple design, its a fine weapon made of many rare materials.

Items needed for remodeling:
Dino Bone     = 2
Moon Stone    = 1
Star Fragment = 2
Screw         = 18

Where to find:
Dino Bone (Balamb/Training Center and Island closest to hell)- From T-Rexaur/ 
Change card into an item, Mug or receive as a battle prize.
Moon Stone (Esthar)- w/Rare Item ability From Toroma receive as a battle prize 
or MUG.
Star Fragment (Deep sea depot and Esthar)- w/Rare Item ability From Hexadragon 
receive as battle prize or MUG Iron Giant.
Screw (Galbadia, Dollet, and Timber)- From Geezard receive as a battle prize 
change card into an item