Lightning: That weapon that raises the ATB bar every attack, and the Lion Heart (unfortunately AFAIK only available in Ch12, Ch13).

Sazh: Pleiades - Hyades. A maxed pair of Hyades Magnums gives incredible Str+, it's not even worth leveling it up to Tier 3.

Fang: Taming Pole. Definitely. Period.

That's what I would choose. Though Sazh shouldn't constantly have the Hyades M. equipped...