You can only undo a death once in your life, so choose wisely. You might pick a lover, a pet, a parent—all reasonable options. Just remember, whomever you undo can (and will) die again, especially if they were in ill health—which is pretty much a wash, especially if you only had a few final thoughts you wanted to communicate to them. Don’t be impulsive like so many teenagers, wasting it on your daredevil friend who went joyriding in their parents’ car and…you know. Nor on a celebrity, because you can bet plenty of other people already had the identical idea.