This is translated from the JP version, some of the weapons in the drop down will be unavailable.

Sharpness+1 always grants one extra level worth of sharpness (i.e. Lv5 at Lv4).

片手剣双剣大剣太刀ハンマー狩猟笛ランスガンランス穿龍棍ライトボウガンヘビィボウガン