Oh! Stuff I know! Bannerfish!
I recently had a major headache associated with picking up a bannerfish. Longfin Bannerfish (H. Acuminatus) are NOT reef safe. However there ARE other species that look damn near identical that ARE reef safe or "reef safe with caution." The Schooling Bannerfish (H. Diphreutes) is perfectly reef safe. As with any butterflyfish, keeping them well fed will reduce chances of them nipping at your corals.
There is also a third species, the Singular Bannerfish (H. Singularius) that is relatively reef safe as well. Again keeping them well fed should keep them off your corals.
Keep in mind that ALL Bannerfish are voracious eaters and will need fed 2-3 times a day.
Also that H. Acuminatus and H. Diphreutes look EXTREMELY similar but there are a few slight differences that can differentiate between them, such as the coloring on the anal fin, the number of dorsal spines, and the shape of it's mouth.
H. Singularius is probably the easiest to identify, if it looks like a Bannerfish but has a FULL black head mask encircling it's snout, it's a Singular.
They're beautiful fish, sociable, very graceful and fun to watch. Mine stays front and center in the tank and likes following the Foxface everywhere he goes.
They're not a hard fish to keep, IME, peaceful, and they don't have a super large tank requirement.
Just make sure you get the right one! The difference between one extra dorsal spine can mean the loss of all your corals. H. Acuminatus will DESTROY your colonies.
I would suggest doing a significant amount of research on identification before going to your LFS. Take printed pictures of the two species with you and get a positive ID before you take him home. Ask your LFS if they know the full latin name of the fish and then double check it. More often than not, you're going to be looking at the non-reef safe variety.
Good luck!