I think either Mismagius, Gengar, Banette, Dusknoir or Rotom and its formes.
darkrai rotom mismagius gengar weezing and dusknoir
ponie
Ghost or dark pokemon
The Ghost-type Pokemon in the HGSS Regional Pokedex are: Gastly, Haunter, Gengar, Misdreavus, and Mismagius. The Dark-type Pokemon are: Umbreon, Murkrow, Honchkrow, Sneasel, Weavile, and Tyranitar.
shiny rayquaza with wondergurad
The best place to evolve a Pokemon in Pokemon Heart Gold is at Mt. Silver.
There isn't Murkrow's Ghost in Pokemon HeartGold. It maybe just a rumor.
There is no best Pokemon on Pokemon HeartGold.
there are many legendary Pokemon in Pokemon heartgold, but the best is HO-OH
Gengar is a ghost-poison type pokemon that evolves from Haunter.
ponie
my mum she is da best Pokemon Eva
It is in Ecrutuk city the leader is morty who uses ghost type Pokemon
Ghost or dark pokemon
first at sprout tower at violet city. next is burnt tower at ecruteak city.
shiny rayquaza with wondergurad
The Ghost-type Pokemon in the HGSS Regional Pokedex are: Gastly, Haunter, Gengar, Misdreavus, and Mismagius. The Dark-type Pokemon are: Umbreon, Murkrow, Honchkrow, Sneasel, Weavile, and Tyranitar.
The best place to evolve a Pokemon in Pokemon Heart Gold is at Mt. Silver.