>>30761929Switching into Normal and Fighting type attacks.
Also for switching out, since they can't be trapped into battle as of gen 6. And for those curious, even if the Pokemon does something that would normally lock it into battle (such as Ingrain), if the user is a ghost type, it's still capable of switching out. I learned this when using Trevenant in the Battle Maison.
They're also for having some of the best overall designs in the series.