If I was still doing this, I would make a prop guillotine for use in snuff and dolcett videos, and possibly bondage and domination videos.
As a prop guillotine, it needs to look real and have a realistic-looking motion, but it should be totally safe, and the performer should be protected from any kind of accident.
It also needs to be made so that from side views, or views slightly angled from the side, there is a clean edge with no gaps that can be used to mask off the user’s head for video effects, and replace it with alternate video (of a head missing, or better yet, rolling off).
It should also be made for sex. It should have a platform that a model can lay on face-up or face-down (I’m more of a face-up kind of guy, and face-up also allows the performer to see the blade coming for her and react). The platform should be built at a height so that a male can stand at the other end and fuck the performer. For face-up sex, some thought should be given to how her legs will be arranged, and if necessary, supported (stirrups?).
There needs to be a lever or pull-rope to release the guillotine. It should be placed such that the performer could release it on herself.
If possible, it shouldn’t be too obnoxiously loud. If that’s not possible, then there will be audio clipping that will need to be fixed in post.