Neutral Density filters are often ignored by photographers, but they have several uses and offer the possibility to achieve otherwise unachievable results. ND filters appear grey and reduce the amount of light reaching the film, they have no affect on color balance.
UV filter is a popular addition to someone's camera kit, often used to protect the front element of the lens from scratches, dirt, water and other foreign matter, and can also make it easier to keep your lens clean, as you can simply remove the filter and clean that instead of the lens.
Slim polarizer filter allows you to remove unwanted reflections from non-metallic surfaces such as water, glass etc. They also enable colors to become more saturated and appear clearer with better contrast.