I am an organ donor, such as it is. Most of my organs are not fit for donation. Fatty liver, slightly hypertrophic heart, LASIKed corneas, lungs damaged by years of reflux until I had the surgery to correct that. None of this is really incapacitating, just makes them unfit for transplant. I suppose they could use my kidneys; they seem okay still.
However, I am also a body donor for plastination:
http://www.bodyworlds.com. So even if they can't use my organs to save a life, I can still be useful after I go, to educate medical students or laypeople for a long time. Finally I can contribute to science.