I use Hoya HD filter (UV maybe- I cant remember) to protect the lens (already saved a smashed lens once where the cap came off unnoticed).
I also have some Hoya polarizing filters, think they are HD too.
And finally I have a nice set of Lee filters- Big stopper, a 6 stop ND and a set of hard grad filters. Comes in handy for landscapes and long exposures. Using filters has nothing to do with not being able to expose correctly!