Deadpool
Deadpool is not a hero. And his relationship with Wolverine is the stuff of legends. So he should appear in the final Wolverine flick. And he should be a villain. Maybe he is hired to capture the hero and his allies? Maybe he is hired to bring X-23 back? Maybe Weapon X tries to get rid of its past mistakes? It doesn't really matter.
Wolverine 3 will be R-rated. And Deadpool would be an awesome addition. Just have him pop-up for a couple of minutes (or not even those). And have him fight Wolverine. Everybody knows how this will end, right?
Oh, the quips! It would be great and you know it!

