Double/lavis cannon and Blade HUcast weapon

[Hrith]

Daggers are better than Double Sabers (especially for males), which is why I'm voting for a much more common and cooler Sinow Red's Blades

I agree on that, none of the Lavis weapon is really worth it.

Demolition Comet, 3rd highest ATP

Black King Bar > Double Cannon > S-Rank Twin > Demolition Comet/Meteor Cudgel.
So it's 4th not 3rd Meteor Cudgel has roughly the same ATP and more ATA, and since I do not like the looks of Demolition Comet, I greatly prefer Meteor Cudgel, which is an easy drop in Whitill, by the way.

But to answer the question, the best lavis weapon is Lavis Blade.

Though, if you have the US non-plus version of the game, an untekked Lavis Cannon is clearly the best.