Well, pretty much all of the mythical creatures in The Spiderwick Chronicles only let themselves be seen by people with “the sight” (or, at least, this was the case in the movie…I haven’t read the books).
Would the aliens in They Live count? They can be seen by anyone, but can only be seen in their true form (at least for the majority of the movie) by the few people who have special glasses.
The Ringwraiths, in The Lord of the Rings, in a sense. Although anyone can see their earthly garments, their faces are invisible to anyone who cannot see into the wraith world.
Constable Benton Fraser on Due South is normally the only character who can see the ghost of his murdered father, Sergeant Bob Fraser, who tries to give him advice in different situations, of varying degrees of usefulness. Also, Detective Vecchio somewhat more rarely sees his own dad, who almost always is trying to get his son to ditch Fraser and “look out for Number One”, usually when Fraser is in some great deal of trouble.
In **Just Like Heaven ** (I know, I know - my daughter was watching it. Honest!) only Mark Ruffalo’s character can see Resse Witherspoon who is sort of a ghost (her character is in a coma).