It seems to me that there are as many " main " issues as there are people thinking about it. Everyone has their own personal position on what is or is not ethical. To me, the basis for all ethical dicisions should be the phrase in the Hippocratic (sp) oath, " Do No Harm".
euthanasia, abortion, saving someone's life after they have continuously attempted to commit suicide, operations for patients who consistently refuse to eat healthily/exercise more/stop smoking/stop taking drugs
just a few examples