You can find wild haunters in Pokemon tower and lost cave.
Get a link cable and trade/receive a Haunter.
you have to traid a haunter
You can trade it to a friend.
in the Pokemon tower in lavender town
No you must trade from FireRed and LeafGreen
Machoke, Kadabra, Graveler, Haunter... Loads...
To get a Gengar you must first catch a Haunter. To evolve the Haunter you have to trade it to another gaming system.
you can't find haunter in Black
Trade a haunter to a friend then take it back to receive gengar.
It won't evolve without trading
Haunter is a ghost type of Pokémon. The last move that it learns in Pokémon LeafGreen version is Mean Look.
machoke - machamp, haunter - gengar and Kadabra - alakazam