[wurmfood]

Ah, sorry, I thought you meant casts that changed state. For the non-interrupt casts, various npcs and group quest bosses have casts that cannot be interrupted.

The easiest examples I know of offhand, though, are all dungeon bosses (black knight, Loken, Anub'arak...).

edit: Looks like transmutes are protected. At least, saronite to titanium is.