Stole this set off of some sucker on Frost, then "modified" it for my personal use. This is one of the most evil sets I've seen in 14 years of playing Pokemon. I use it on my mono fire team and it's brilliant. Anyway, here it is:
Ear strike (Delphox) @
EVs: 96 HP / 8 Def / 144 SAtk / 8 SDef / 252 Spd
- Hidden Power Ground/ Hidden Power Rock/ Psychic/ Psyshock
The plan is simple. Send Delphox out as a lead and use substitute. If the opponent attacks, then red card swaps them out. If they try to set up, then either substitute blocks them, or they boost up, making it hurt that much more when red card forces them out. So far so starightforward.
So the opponent's next poke is dragged out. This is where it gets interesting. Delphox uses will-o-wisp to burn them, and magician steals their item at the same time, crippling them in two ways at once, and boosting Delphox in the process (the item stolen is almost always leftovers). This is absolutely devastating against more physically oriented teams and tanks. With substitute and it's evs, it can burn half a team before being put down pretty easily. The last two slots ensure that Delphox isn't taunt bait and has a tool to use against Pokemon that can't be burned. Flamethrower is the prefered STAB for it's higher pp and accuracy over fire blast. the last move is filler. Psychic is a decent move to hit things of it's other STAB quite hard. If you anticipate things like Houndoom and Heatran then HP rock is the prefered hidden power, especially against things like Moltres.
It's Hp and very minor def and sp.def evs are enough to let it take hits behind subs pretty well, and take burned physical hits and special attacks comfortably. The Sp. atk evs give it a nice total Sp. atk stat of 300, enough to do good damage to anything that doesn't resist it's two attacking moves, while burn damage racks up (if staying in) or when pushed into a corner or cleaning a team of weakened mon. The timid nature and speed ivs are so that it will almost always get it's sub up before taking a hit, and firing off its magician will-o-wisps before the opposing Pokemon moves. It is vital.
Now, for the downsides. The primary one is that while Delphox can enter the field and sub up with great ease, and the burns and bulk can help it stay alive for quite a while being a hellish nuisance, the opponent is obviously going to be doing stuff too. First and foremost, the boost to infiltrator and sound moves, especially bug buzz, will allow several mon to derail this strategy quite a bit (recommend HP rock for Noivern, chandelure and Crobat, by the way).
Also, while boosting sweepers are no threat at all if Delphox gets it's sub up (and look downright silly when they hit a sub with a +6 earthquake and have to switch out) , entry hazards are more of a problem. A spinner is definitely recommended to get rid of any hazards set up after Delphox is done. This isn't a huge issue, though, as Delphox can bag the premium OU rocks users and spikers (skarmory, Forretress, Ferrothorn etc.) with a few well timed attacks and burns.
Finally, and most crucially, beware of what you're burning. Red card drags out a purely random mon. This means that Delphox could easily steal a choice band and cripple itself for the rest of the match, along with its opponent.
Also blah blah stealth rock blah.
Other useful possible moves on this set are wish, trick and mystical fire. use whatever you want.
So in short, what you have here is an excellent, surprisingly hard hitting, fast and downright sadistic Pokemon that offers great utility and opponent-crippling. BUT it does take skill to use at times. Use it well, and it can make your team mates jobs a whole lot easier.
This set really does work, though. I've been using it on my OU gen 6 mono fire team. It's been winning a lot since I started using this thing.
Heh. Text wall.