Obviously, living a long time is the first that comes to mind. That doesn't really give you the game mechanics of coming back after you "die" but it works. In ICONS and Mutants and Masterminds, buying Life Support (aging) does this just as well as Immortality. If you want a cheap way to live forever and still have the risk of dying, Life Support is the way to go.
Some kind of treatment, whether it's the Lazarus Pit or implanting monkey glands or full-blood transplants of the blood of superheroes is the next. It might or might not provide some kind of regeneration.
Next is serial possession. The spirit is immortal and leaps from body to body. There might be limitations--maybe the victim has to be a blood relative, or a particular kind of mutant, or a baby, or a clone. Planting your mind in a clone (a la John Varley) counts. (I can imagine a very creepy family where everyone knows that they might be taken over by great-great-grandfather for his next body. Some of them might be deliberately slothful, trying to make sure that their body isn't the next one that gggf will want; some of them actually want to die, so they're playing the "fitness=death" lottery; and one of them is hunting great-great-grandfather to kill him and claim to be the current host.)
Maybe the host comes to look like the original. In some ways, they will: the immortal spirit probably has habits that affect the body. ("So, Lucy, when did you take up smoking cigarettes?")
Imagine duplication where the duplicates are the age when the power first manifested. The original eventually dies of old age, but a duplicate (if one is split off at the time of death) "becomes" the original. And so on, and so on.
Can you think of others?