Guys, any kind of VG focused speculation belongs in the VG News & Discussion forum. Only post threads in General Pokemon Discussion if they cover multiple mediums in the series (games, anime, manga, etc.).
Anyway, I've come up with a couple of interesting ones, mainly designed for hypothetical Megas:
Corrosive: This Pokemon's Poison type moves are super effective against Steel types
Pokemon that have it: Mega Muk, Bellsprout line, Mega Swalot
Sticky Mud: Mud moves (Mud Slap, Mud Shot, Mud Bomb) can hit Flying types
Pokemon that have it: Mega Quagsire, Barboach line (replaces Oblivious), Stunfisk (replaces Limber)
Deadly Venom: Any move that would Poison the target Badly Poisons them instead
Pokemon that have it: Mega Seviper