I have not thought of a moveset for my dusknoir well , here it goes ...

Nature : Bashful
Will of Wisp
Thunder Punch
Shadow Punch/Shadow Sneak
Confuse Ray/Trick Room/Pain Split

What's Bashful again? Well, a nature that's +Defense/Spec. Defense and -Speed is good. A set might be:

@ Leftovers
EVs: +Defense and Spec. Defense
Nature: +Defense/Spec. Defense -Speed
Ability: Pressure
Will-O-Wisp
Shadow Sneak
Trick Room
Earthquake

Or try a set revolved around sweeping, as Dusknoir has some ability to sweep.

@ Leftovers
EVs: +Attack and Defense/Spec. Defense
Nature: +Attack -Speed
Ability: Pressure
ThunderPunch
Shadow Punch
Trick Room
Earthquake

The tank set (1st one) should be more perferred, but it's predictable. If you want to cast some surprise, use the sweeping set.

Good luck, soldier! Hence forth!

{Dusknoir} Leftovers
Impish nature
EV's HP + Def

Moves~

Night Shade
Fire Punch/Ice punch
Will-o-Wisp
Pain Split

Night Shade to round out some damage, pain split to recover [It's really effective against tanks with lots of HP] will-o-wisp to take some damage out of the other team, and F-Punch your way out of a tight spot :] Max out HP Ev's because Dusknoir has a terrible HP stat. I used Dusknoir to counter Rapid Spinners, because the spinners are usually bulky pokemon, and I can abuse Pain Split

As far as EVs go 252HP is best for tanking unless you want to overly abuse pain split. EVs in Def/S.def can be evenly split with a silde into S.def as Dusknior can "boost" his def with WoW. Attack EV's are ok, and are best used on a mostly offensive or choice band set. Naturewise any -speed nature works well on him depending what you want.

The movesets above look good, Spite+Pressure can PPstall very well, taking 6PP a turn. Combining it with protect can bring it to 8, killing a 8pp move can ruin some choice sets. Rest-talk sets are also effective.

building off Master Chef's words:
just thgink, the Hail/blizzard combo is alive and well, you send out the PP burning dusknoir and the blizzard combo falls short at that momet, powerful elemental moves are stoppe din their tracks and ur opponent can do nothing to stop you!!1