Scotland and Hawaii :)

I don't think I have any ideas which would require location research. Most of my fandoms are set in fictional locations anyway.

Though I would research a location if it was a real place I wasn't familiar with. I've come across stories before where it's so obvious that the writer had no idea what the place was like - in one case, writing it like it was a medieval city - and it wrecked the story. There's also always the chance that a reader could actually live in the place you're setting the story.