Here's a personal favorite one of mine, the Whirligig Saw from Bloodborne's DLC. This is both in its untransformed and transformed forms, but as always it's only a model port.
It replaces the Knight's Greatsword in the untransformed state and Ghiza's Wheel in its transformed state (obviously). The regulation.bin alters the moveset of Ghiza's Wheel so it is more reminiscent of the original Whirligig Saw moveset.
Password to the file: Bl00db0rn3_Wh1rl1g1gS4w