I'm going to be a bit morbid here, but of all the diseases or mechanical ways to die, which would be your LAST CHOICE if given a preference. Dead last, so to speak.

Milk and honeyed to death, if you know it, you know that shits barbaric.

If we talking in the realm of realistic and probable, probably Alzheimer's, or maybe being trapped in a vegetative state but concious and lucid.