A clean and highly visual penetration effect, which you can perform on a large stage or even a drawing room, completely surrounded by the audience.
The performer displays a Neck block, that imprisons the neck, and a sword, that passes right through it. The sword can be demonstarted as rigid, (swished in your most cavalier manner), and sharp, (slicing pieces of a banana). A sporting, though reluctant lady spectator is coaxed into participating in the "experiment".
The neck stock is placed around her neck. The sword is pushed right through. It emerges at the opposite end, as the lady smiles, and her mother swoons !
Then remove the sword and stock to show there isn't even a smear on her make up ! Quality props, with stainless steel sword and scabbard (you wouldn't keep a naked sword in your pocket !), and the mechanical neck block that makes the illusion possible.