Base Haunter...Not too bad but to do any damage the opponent has to be asleep.  Well if you combo Haunter with Rocket's Goto Sleep(Sleep Sleep, Sleep Gas, etc.) then you dont have to flip 2 times to do damage.  Just once.  This combo may be used a lot in April-May(or whenever Rocket comes to America). 
However, nothing can replace Fossil Haunter, what can i say but WOW.  Takes down Mimes easily, keeps Blastoise from Dancing and stops Haymakers in their tracks. 
Fossil Gastly is a great opening Pokemon also, 10 damage and possible Paralization, Free Retreat and 50 HP...thats very high for a basic w/ evolves.  And just slap another energy oh him turn 2 and evolve him, you can chose to or not to goto Gengar(2nd greatest Fossil right behind Haunter).
Fossil gave Psy decks a great chance.  And Mewtwo(Movie) helped a lot too.
But when the 2 Haunters go at it.  Fossil would probly win, all of those coin flips for asleep, Trans., and Nightmare.  Any way you go, Haunter will win ;-)
 
Daniel Perdue
neopolatin@earthlink.net