With the K10D, you can apply several digital filters to your photos after you have taken them. Black & white and sepia come to mind.
It is really easy to convert your colour photos into B&W using digital darkroom software. This gives you the most control. Pentax has included an in camera feature that will do that for you however if you so wish. Consider this a nice bonus. It is not something I would use, but to each their own as there is some debate on the benefits of in camera filters as opposed to out of camera filter applications in regards to file saving and JPEG image degradation.
I know this may be slightly off topic, but you may be interested in this tool. I like this one a lot, and of course it is free. It is called Opanda Photofilter 1, a free standalone program that gives you a nice range of Kodak, Cokin, and Hoya filters for your photos. Indispensable, and quite fun to run some photos through the list to see the various effects. It sort of beats having a bag full of filters at times.
Opanda PhotoFilter - Professional photography filter imitation software