B&W filters are always a good bet. FWIW, this lens has no vignetting issues even with normal thickness polarizers at 24mm, so you don't need to buy thin mounts for it unless you plan to stack filters. FWIW, I'd advise not using a UV or clear filter just to keep the front lens element clean unless you're in some exceptionally harsh environment. It's a great lens and adding a filter for no particular reason can't help image quality.