Considering that salt and pepper shakers aren't used to eat food with directly, nor are they used to make food, do they have to be immersed in a Mikvah before using if they are ceramic?
According to the Orthodox Union,
askmoses.com, a saltshaker needs immersion, and that need is definite enough that we say the b'racha on the immersion. However, that's assuming it's of metal (or glass). According to those pages, unglazed ceramic/earthenware does not require immersion and glazed ceramic (porcelain) requires immersion, but without saying the b'racha on the mitzva of immersion; but I know some don't require immersion for porcelain. As always, contact your rabbi for practical advice.