Apparatitions/Body Doubles/Ghosts/Avatars

Locke - Smokey/Locke
Walt (still alive, seen by Shannon)
Charlie (seen by Hugo)
Boone (seen by Locke, or was that while Boone was alive, Locke saw him dead?)
Christian (seen by Locke, Jack, Claire)
Yemmi (seen by Ecko)
Libby (i thought she was seen as an apparition, but i may be wrong)