Perhaps you're asking about Pokemon that are Ghost-type, meaning they have the Ghost type as one of their types. Here's a list of all Ghost-type Pokemon:
Generation I
* Ghastly
* Haunter
* Gengar
* Gastly
* Sableye
Generation II
* Misdreavus
* Murkrow
Generation III
* Shuppet
* Banette
* Duskull
* Dusclops
* Drifloon
* Drifblim
* Snorunt
* Glalie
Generation IV
* Spiritomb
* Gible
* Gabite
* Garchomp
* Mismagius
* Rotom
* Frillish
* Jellicent
* Yamask
* Cofagrigus
* Chandelure
Generation V
* Litwick
* Lampent
* Chandelure
* Solosis
* Duosion
* Reuniclus
* Golurk
* Hydreigon
* Gothita
* Gothorita
* Gothitelle
* Frillish
* Jellicent
* Mienfoo
* Mienshao
Generation VI
* Trevenant
* Gourgeist
* Phantump
* Aegislash
* Honedge
* Doublade
* Spiritomb
* Dedenne
* Carbink
* Duraludon
* Grimmsnarl
* Gengar (Mega Evolution)
* Gengar (Gigantamax)
Generation VII
* Mimikyu
* Dhelmise
* Decidueye
* Palossand
* Silvally
* Gengar (Gigantamax)
* Runerigus
* Dragapult
* Cursola
Generation VIII
* Greedent
* Impidimp
* Morgrem
* Grimmsnarl
* Hatterene
* Glastrier
* Spectrier
* Calyrex
* Calyrex (Ice Rider)
* Calyrex (Shadow Rider)
Generation IX
* Greavard
* Houndstone
* Tandemaus
* Maushold
* Palafin
* Brute Bonnet
* Flutter Mane
* Iron Bundle
* Sandy Shocks
* Iron Hands
* Kingambit
Let me know if you'd like more details about any specific Ghost-type Pokemon!