Dusknoir Nature: Adamant. Item: Leftovers. EVs: 252 HP. 252 Attack. 4 Sp.Def.
Shadow Sneak hits psyhic and ghost type Pokemon for the super effective damage, Aquires STAB. Priority move is very nice to have on a team, It can finish off weakened opponents.
Brick Break certainly has its secured spot here, There is no Pokemon at all that recists both the Ghost type move and the Fighting type move.
Altough Ghost/Fighting provide at least perfect neutral coverage, We still have the Bug/Steel types not to mention the Flying/Normal type which Dusknoir can have some trouble taking down, Not to worry, This Ghost gets the elemental punches.
Ice Punch hits Gliscor, Dragons, among some other types. Thunderpunch is also an option, It can be nice to have an electric type move on a team.
Dusknoir's HP not being that good, Pain Split does work well though might not be that reliable so Earthquake is also an option.