Toxicroak

Copied from ONM

SuckerCroak $oily
Toxicroak@Focus Sash

Jolly (Or Adamant, but you won't be outspeeding much)
252 Atk - 252 Spd - 6 HP

Sucker Punch
Swords Dance
Earthquake/Stone Edge
Cross Chop

What it Does:
Best used as an opener, the plan is to Swords Dance until you're hit (Focus Sash guarantees a Swords Dance) and if you aren't hit carry on Swords Dancing. If you were the quicker opponent when Swords Dancing then use one any of the moves given, however, if you were slower risk it with Sucker Punch. It's rare that anyone will realise what you are doing since Toxicroak is rarely used in the metagame and after 2 or 3 Swords Dances you can OHKO most things. I use this a lot in my battles.

How to Beat it:
Knock it down to 1HP when it's Swords Dancing, when it's about to Sucker Punch switch to a status Pokemon and Burn or Poison it, alternatively you could bring out a Hipowdon and Sandstorm it to death, or Abomasnow.

Wow, this set is really, really good! xD

Nah, there's probably loads of flaws in there but I've been using this as an opener for a good few months now and it almost always OHKOs at least one member of the opposing team. It's even better if the opponent hasn't got a clue what Sucker Punch does, I swept a team 6-0 with it xD

You seem to be massively underestimating people there. Don't assume that your opponent won't know what you're doing.

Jolly is the better nature, since SD will give you all the attack you need. Also, what will EQ hit? Cross Chop hits Steels and Stone Edge hits Fire types. It'll hit poisons, but most common Poisons in OU have Levitate.

For the Counters section, Skarmory does a pretty good job as it can either Whirlwind him or kill him with Drill Peck / Brave Bird. Bulky Ground types can come in easily enough and EQ him to death. Anything with W-o-W will also cripple him. Anything faster than him that won't die to Sucker Punch can stop him easily too.

Earthquake is more likely to be used than Stone Edge really, you can't afford to miss when you have such poor Defence and you're probably going to be on 1 HP. Cross Chop is there for STAB but can be replaced by X-Scissor which is good for when your opponent realises you're Sucker Punching and decides to switch out a Calm Mind Cresselia etc. Poison Jab can be used for... uh... Grass types and STAB but the other options are more likely to be used. Pursuit can be great for other Psychics but you'd have to get your timing and predicting right. Also, there's Bullet Punch for anything faster than you that resists your other moves.

There's also alot of counters for this set but you're best chance is to lower its health to 1 HP and switch to Hippowdon, it resists Stone Edge and Poison Jab and Toxicroak learns no moves that are SE against it. Also, Hippowdon can Curse up in the turn that Toxicroak attempts to attack. Sanstorm will finish it off.