I'd be relatiely surprised if this hasn't been posted before, but then again I suppose Skuntank is NU and might not get too much attention. Anyway, if Spiritomb runs half of the same moves and has 2 inferior moves, I think this deserves to be in the analysis, or get some recognition.
Cat-22
(yeah, he's going to piss all over your team)
Skuntank @ Life Orb, 252 HP / 252 ATK / 6 DEF, Adamant
Sucker Punch
Pursuit
Fire Blast
Explosion
The core of this set is pretty obviously the Pursuit/Sucker Punch combination, from which the name is derived. This combination was famous back near the start of the D/P metagame, has all but died out recently due to it's only other user, Spiritomb, falling out of OU, and lacking the real power to pull it off (none of the listed sets for Spiritomb really have the attack EV's to make the set worthwhile in much apart from azelf), going for defense above offense.
This is where this set shines however - with max attack and LO, Skuntank reach 407 attack, giving the most powerful Pursuit (bar CBTar, LO/CB Weavile and LO Honchkrow) and Sucker Punch (bar LO Honchkrow, CB Slaking, LO Absol). Unfortunately, surprise does factor in to part of the effectiveness of this combo - after seeing both SP and Pursuit the opponent will likely know what's up and try to mess you up, but that's part of the fun anyway =). Just for an idea of power (against possible counters that won't be exploded):
SP vs 4/0 Flygon: 58.9% - 69.9%
vs 4/0 Salamence: 53.8% - 63.7% (destroyed with a scizor also on the team)
vs 252/168 Rotom: 71.7% - 85.5% (the most defensive rotom, although it carries will-o-wisp, which messes up the set)
Naturally, off 407 attack this combo annihilates scarf Rotom, any form of Latias without reflect, azelf, gengar, and does about 66% to fleeing scarfed Uxie.
Now, I say exploded, as Explosion is carried since the above combo can't kill everything. Off 407 attack, it becomes the most powerful physical attack that you'd normally find in OU, bar the rare CB Snorlax SD. Whole scores of pokemon are killed off - basically anything that isn't boosted, Rock, Steel or Ghost (but you'd be silly trying them after seeing the first two moves). And even then those pokes are struggling:
Explosion vs Tyranitar 4/0: 83% - 97.7% (vs 252/0: 70.3% - 82.7%)
vs Metagross 4/0: 74.2% - 87.4% (vs 252/252: 50.5% - 59.6%)
Finally, you'll see Fire Blast. You might be wondering why a special attack with an adamant nature and no special EV's, but that's the beauty of Life Orb. This move is saved for the last 3 important steels that don't mind too much the above attacks - Scizor, Skarmory and Forretress. With Stealth rock on the field, the only way Forretress could ever survive is 252/252 S.Def +S.Def nature - any other nature and it's dead. Since you might have guessed, this is pretty rare, so nothing to worry about. The same almost counts for Skarmory - with a S.Def nature (the only real way it'll not be 2HKO'd), it has no chance of outspeeding Skuntank, who'll keep FB'ing until it's dead. Also, the chance of burning isn't too far from the chance of missing, which'll speed along the death. Scizor is obviously a goner.
Speaking of Scizor, it's surprising how many people put him in after the first kill and expect a similar revenge kill. The only way it will ever do this is after SR, LO damage, and Scizor must outspeed and use Bug Bite. Again, thanks to the rarity of Skuntank, they're not expecting how buly this set is, nor that it may have Fire Blast, so they're most likely to BP (whick the skunk laughs at) or swords dance, which again is laughable again.
Even with no EV's in speed, at 84 base, most tanks are outsped (as well as usual CB users) and exploded on. The EV's are pretty obvious - max attack and the defenses. The super-bulky physical attackers will usually carry earthquake and can be switched out on (and even if they kill, there's the wonderful Aftermath ability which can hit through subs), and the harder hitting special attacks are usually Dark-weak, or slow.
In all the time of useage, I've found farely few counters, but these are Lucario, bulky Rotom, fast T-tars (if I know they'll DD, boom), Metagross, Salamence and Dragonite.
