If you want to kill yourself using an automobile that does not include your garage or other enclosed space..
The smart car is the smart choice for a collision death.
They are tough cars that transfer all the crash impact through the body of the car and up the seat in to you.
You however do NOT take a crash well and the end result is death. (normally)
Here’s an interesting report on the death rate per million miles by make and model. This is info usually buried because it confirms what common sense might tell you. (I don’t see Smart cars among the worst, but I haven’t looked for a reason):
http://www.iihs.org/iihs/sr/statusreport/article/50/1/1