Scizor #212

Harasser 
Name: Scizor

Item: Choice Band
Ability: Technician

- Bullet Punch
- Pursuit

- Superpower
- U-Turn
EVs: 252 SDef / 200 HP / 56 Atk

Nature: Adamant (+Atk, -SAtk)


Moves:

Bullet Punch is the best STAB move with Technician and a priority move.

Pursuit to hunt down Psychic and Ghosts with choice items, thanks to Scizor's ability in many siatuations it's like "damned if you will, damned if you won't" for your opponents switches.

Superpower good to deal with other Steel types and also some Dark and slow high def Rock, Normal and Ice. 
U-Turn great scout move while harassing fairly well with STAB.

EVs & Nature:
Adamant to get more Atk damage, which is Scizors greatest stat.
As any Choice Band build this build is going to be switching around, and since we can have Bullet Punch, it is better to invest EVs on survivability (for entering hazards) than on speed. Since Sizor is going to fight in OU and Uber environments 252 SDef is really important.
Instead of 200 EV on HP it is also possible to run 104 HP and 96 Def to balance its defenses, but I find it worse most of the times.
The 56 Atk EV plus Adamant keeps your Atk as the highest stat and is enough to avoid an extra attack for some KOs.

Gyarados #130

Scary Dancer

Name: Gyarados

Item: Leftovers
Ability: Intimidade

- Waterfall
- Dragon Dance

- Stone Edge / Ice Fang
- Payback / Taunt / Dragon Tail
EVs: 252 Atk / 172 Spd / 86 SDef

Nature: Adamant (+Atk, -SAtk)

Moves:

Waterfall is the best STAB and all around attack.

Dragon Dance to set up versus switches and attack first.

Stone Edge a bit coverage against Grass and Dragon, but shines versus Flying and Water resistent. Ice Fang is a good alternative but has lower base power.
Payback/Bite to cover Psychics that resist water like Starmie, Celebi and to a lesser extent Ghosts. I personally prefer Payback over Bite, as your opponent might be passing some speed boosts or have Choice Scarfed which will outrun this build with +1 speed (exº Ninjask passes to Starmie). Bite doesn't allow you to KO with 1 less hit comparing to a normal Payback. 
Taunt is useful for stopping slower pokemons from using Stealth Rock, Spikes, stat boosts, healing. But in this case it's speacially good to stop PHazers trying to cut your sweep.
Dragon Tail is you knew Roar, that also happens to help versus sweeping Swords Dance Salamence, or predict a switch into an Electric user while stacking passive damage.

Other moves:

Bounce also sees some play to let Leftovers recover and anything that switches to resist might get paralized, but I personally don't like 2 turn moves.
Sleep Talk is also a funny gimmick if you don't have a sleep absorver on your team.

EVs & Nature:
The major difference between Gyarados is it's stat distribution. With this Dragon Dancer build I focused on outspeeding jolly Starmie after a +1 speed from Dragon Dance and every pokemon around that speed. This is important since I manage to take the expected Thunderbolt while keeping the Atk at its max killing Starmie 1v1 and other fast threats.

Infernape #392

Leading Ape

Name: Infernape

Item: Focus Sash
Ability: Blaze

- Fake Out
- Stealth Rock

- Close Combat
- Fire Blast / Overheat
EVs: 252 Atk / 196 Spd / 62 SAtk

Nature: Naive (+Spd, -Def)

Moves:

Fake Out, starter move, major role is to get free damage while cuting opposing Focus Sash. Beware of pokemons that might have Inner Focus, speacially Lucario and Dragonite, you don't want to use it versus them.

Stealth Rock with Fake Out + Focus Sash it garantees that you cut opposing leads using Focus Sash and you always have a chance to Stealth Rock cutting further ones while you start dealing passive damage early on.

Close Combat your main STAB attack, you'll be using this as your default attack, great damage and accuracy and supper effective versus many OU leads and walls, the drawback doesn't affect you at all with this build.

Fire Blast is the usual pick for steady damage, but you should consider Overheat for higher dmg on 1st attack and better accuracy, specially if you expect to die soon or switch out. Don't forget the 50% Blaze bonus after Focus Sash activation. In many cases I prefer to burn out than to "fade" away ;)

Other moves:

If you need a better Infernape on mid game to counter some threats to your team you can adapt usually at the cost of Fake Out or Stealth Rock.

Taunt is useful for stopping slower pokemons from using Stealth Rock and Spikes. It also stops stat boosts, healing and PHazers.
Mach Punch is nice versus Focus Sash Lucario if you expect to see those.
Stone Edge versus Dragons and Gyarados.
Grass Knot versus Water.
U-Turn good scout move and hurts Psychics, worth a mention against Starmie and Latios/Latias.

Counters:
Usual bulky water pokemon. Since you should already have Stealth Rock up, don't mind the switches and get a counter on your team ready. Special attention to Starmie, as it resists your 2 STAB moves and can clean your Stealth Rock with Rapid Spin.
Dragons pose a big threat if you don't have Stone Edge, but they probably won't risk it if you have Stealth Rock on. If they do switch.