Omastar
Mudkip
Swampert
Marshtomp
Dragonite
Magikarp
Still, in fifty or so years, there'll probably be a fan fiction where Magikarp acts like Godzilla while being brainwashed by a certain villain, and destroys the entire world. Maybe Game Freak would rip off of that (they're ripping off of stuff already) and have the Distortion World and Citrus the Team Galactic leader make a reappearance. At that point, Citrus would probably have all the stuff he needs to make his own little world, and the player, who ends up in the Distortion World due to being knocked out, has to put everything right before the Lv 100 Magikarp returns.
It may sound ridiculous with Magikarp, but if you make it a Godzilla-Metagross, it would make the storyline a bit more plausible.