How about that nifty power where you become a one-with-the-Force ghost when you die?
Or Sidious' "stop people from dying" power?
Or Palpatine's "transfer life" power he used in the EU to transfer himself to a younger clone?
First One - 100% plot device
Second One - Sidious was lying out his arse to con Anakin into joining him
Third One - Plot device from a really asinine story that largely undid the bulk of Vader's sacrifice and Luke's personal journey in RotJ.