Personally, I want my closing scene to be a peaceful and tranquil affair and part of my current plan involves taking extra steps to prevent any vomiting post-unconsciousness and minimise any convulsions or incontinence and leave my body in a reasonably salubrious state etc.
If I did want to cause havoc though, I'd be thinking about the people who would be finding my body and potentially designing it as an experience. For example, one of the common hazards of death by electrocution is that first-responders instinctively touch the body and receive a shock themselves (which is usually non-fatal, but it surely adds to the terror of the experience).
If you have some DIY skills then a fairly gruesome death could be achieved by building a contraption on the basis of a simple pulley and weight system. I read a case report some years ago of a man who bolted a metal spike into the floor of his workshop and hung a heavy weight above his head on a pulley, when he cut the rope the weight dropped and impaled his head on the spike, driving it into his brain (he presumably lost consciousness almost instantly).
Using almost the same system a number of people have constructed home-made guillotines or weighted blades like daggers or knives, these are the kind of unusual suicides that make the news and almost inevitably get written about in the medical/forensic literature as well. With a little additional construction work one could even construct a number of guillotines, each consisting of a simple pulley system, a weighted blade and some guide rails, they could all be affixed to the same stanchion and when you cut the rope (or perhaps employ a more elaborate timer system like the flame of a candle) - the blades drop and your body is sliced into pieces - perhaps one individual piece to represent each of the people in your life who ripped your soul apart.
Just some ideas, perhaps not particularly practical for someone without construction experience. Taking it a step further then, let's imagine that you also set up a webcam to record a live-stream (a fixed-length video recording to capture a brief video suicide note and then the process of your actual death). Once the webcam has finished recording let's say a ten minute time period, then post-mortem a script on your computer takes the finished video recording, uploads it to your Dropbox or whatever and emails a link to the people you want to haunt.
Innocently, they click the link and the true screaming horror of decapitation and mutilation shocks them to the core. These ideas are becoming increasingly dark, which is quite unlike me... But then again, I was inspired by the dark passion in your original post!
