It's not really horror (though it does involve witches), but Will Ferrell has agreed to play Darrin Stevens in "Bewitched". The upcoming movie remake of the 60s TV show is written and directed by Nora Ephron ("When Harry Met Sally"). Nicole Kidman is expected to play Samantha, the witch who gives up witchcraft to become a mortal's suburban wife.

The movie has just been announced, and is expected to be released sometime in 2005.

Source: Hollywood Reporter [1]