My absolute, #1, soul-implanted favorite movie of all time. I know it by heart. Any movie that has Terry Thomas exsanguinated while he watches a porno is sweet deliverance perfection.
The constricting frog mask scene is my favorite. Dr. Phibes Returns is a much more stylish film (his Rolls-Royce coffin is awesome 70s camp-nostalgia), but the first one is the one I fell in love with.