I love Hackmons, and it is what drew me to Showdown in the first place. I've had a good amount of experience with Balanced Hackmons, but not regular Hackmons. The strategy should still remain the same.
Deoxys-S can use any one of four abilties to do huge damage to the foe.
As it is the fastest Pokemon in the game, it's Pranskster goes before any other, allowing it to give the fastest Prankster Spore.
It has the fastest No-Guard Sheer Cold in the game.
It can use Mold Breaker to Spore through Magic Bounce.
And it can use Magic Bounce to reflect Spores and set up Hazards to take down Wonder Guard users.
Imposter Blissey, as Blissey has the highest HP in the game (Imposter only keeps the HP stat.)
Huge Power or Pure Power Slaking. No more Truant. And incredibly high stats. STAB Extremespeed. The thing is a bulky menace.
Wonder Guard Spiritomb. Wonder Guard+Air Balloon on an Electric type or Dark/Poison type such as Drapion. I believe setting up a Substitute makes this invincible along with Magic Coat, which stops phazing. Air Balloon also helps protect against the one weakness of these Pokemon, Toxic Spikes.
While I haven't seen much this used, an excellent strategy that Zach told me about is Pranster Restalk with phazing moves Dragon Tail and Whirlwind. Since there are some incredibly bulky Pokemon, this becomes very viable, especially with hazards.
Having Shadow Tag is always popular, as with a Set-up attack from a bulky Pokemon, you can easily win the game (after taking out Blissey, unless you also have a Sub in the set.) I once used Acupressure to get to +6 in all my stats, and then swept, just because I used a Shadow Tag Giratina on the first turn against Deoxys-S (watch out for the Mold Breaker Deoxys, this strategy only works 2/3 of the time in BH. Also make sure to use Magic Coat on turn one against Spore!)
Contrary with V-Create or any STAB -2 Attack (Psycho Boost, Overheat, Leaf Storm) is pretty awesome. Reshiram is a popular user of Contrary Overheat.
Always remember to carry around a Pokemon with Mold Breaker, as it is sometimes the only thing that can defeat a Wonder Guard Pokemon. Sand and Hail also help with this.
As for Simple Smash Passing, Baton Passing is a waste of time when every Pokemon can learn any move. That isn't to say Simple is bad though. Try Simple and Tail Glow for an instant +6 boost.
For Balanced Hackmons, remember Pure Power, Huge Power, OHKO attacks, and Wonder Guard are banned.
I haven't gotten a clear answer to anybody on Showdown about this, but Moody might also be used with a stall set similar to what we saw with Bibarel at the start of BW. I don't know if it is banned though in Balanced Hackmons, so get a clear answer before using it.