Some deaths I would do (and some jokes):
1. Wonder Woman whilst saving a man.
2. Bruce Wayne of old age.
3. The Joker by forced suicide. I would want him to finally go all out, and when he fails, have a backup plan that allows Batman to be forced to kill him, but also in a comedic way. Before The Joker would be killed, we'd find out his real name and Batman would share a laugh with him and a handshake. (I know the handshake seems really out there, but I'd like to see it happen without the electrical shock and such, because they really do have a mutual respect going on and they're one in the same. In my mind, it would kind of seal Batman's old problems and help him move on.)
4. Kyle Rayner would get so old that he would become a Guardian and spend the rest of his days like that.
5. Galactus would become a Celestial and completely change his personality.
6. Grundy would just go back to the swamps and never be seen again.
7. Hawkman/Hawkgirl/etc would die in a plane crash haha.
8. After some plot that he would have to destroy Gotham, Ra's al Ghul would have a discussion with Batman, and eventually be convinced that Bruce will change Gotham for good. Ra's would sacrifice himself to stop his own plot and SAVE Gotham.
9. The Thing would sit in a pool and erode to death lol.
10. Plastic Man, Elongated Man, Mr. Fantastic, and all of them would all be rolled into a giant rubber band ball lol.