I'm going to butt in here and mention some very good pokes that I've been trying out... Since many of them are so Nu they aren't even really NU, I can usually wreak serious havoc.
Dusknoir @ Assault Vest
Ability: Pressure/Frisk (whichever one suits your purposes)
EVs: 252 HP / 252 Atk / 4 SpD
Adamant Nature
IVs:
-Shadow Sneak
-Eathquake
-Rock Slide
-Payback/Fire Punch/Ice Punch/Sucker Punch
Dusknoir, which is so often used for defensive or utility sets, can also be utilised as a VERY GOOD TANK. It's special defense and defense reach nosebleed levels with the combination of EVs and Assault vest, and its already passable 100 attack stat can be used in tandem with its wide range of physical moves:
-Rock Slide + Earthquake: The obvious "EdgeQuake" type-coverage combo for large amounts of coverage.
-Sadly, Shadow Sneak is the highest BP Ghost physical move Dusknoir can put to good use (Shadow Punch is just too weak), however, it does partially patch up its abysmal speed.
-The last moveslot can be anything, really. Since Dusknoir is virtually impossible to OHKO, it can use Payback/Sucker Punch to hit other ghosts relatively hard, and the Fire/Ice Punches also offer good coverage (although I prefer Fire).
Another good unexpected threat I've found is Shiftry. Shiftry thrives in NU--so many Eviolites (Doublade, Gurdurr), Lefties, and Scarfers are running around that it is Knock Off Heaven. And the best thing is that Shiftry is super-unpredictable--it can run a physical or special set, although I prefer physical to get more Knock Off power. Its vast movepool, which includes gems such as Leaf Storm, etc. can even allwo it to be used as a Specs/Scarf user itself :)
however it is destroyed by U-Turn s its best to kill any Scarfers on the opposing team before attempting a sweep
Shiftry @ BlackGlasses
Ability: Early Bird
EVs: 4 HP / 252 Atk / 252 Spe
IVs:
Jolly Nature
Moves:
-Knock Off
-Sucker Punch
-Seed Bomb
-Rock Slide / X-Scissor / Low Kick
Knock off b/c you know ;) Sucker Punch for Priority STAB, Seed Bomb for the only strong physical grass move it gets, and a variety of coverage moves for the last slot.
Anyway, as per now I think the biggest threats are basically Doublade and Wormadam-T. Ask me why if you really want to know (but im sure most already do)