This was a team that I randomly whipped up and worked for me in the range of 1800s in Pokemon Showdown.

Talonflame - Choice Band
252Attack/252Speed/4Hp
Ability : Gale Wings
Nature : Adamant ( I'll explain this later on ) / Jolly
- U-turn
- Brave Bird
- Flare Blitz
- Steel Wing
In this meta, where Fairies currently show huge dominance against the dethroned Dragons, I prefer Steel Wing to rid of them. U-turn serves as a great scouting tool with Choice Band, able to at least put out some damage before returning. Brave bird, as I tested in PSD, deals a OHKO on Sweepers and a potential 2HKO on Defensive walls. With the Gale Wings ability, this allows you to move first and deal a choice banded Brave Bird with STAB damage. Flare Blitz, aided by max EVs in Speed, gives Talonflame a huge advantage over it's type advantages, which are usually slow. However, despite it's great attacking prowess, you have to remember this guy is merely a kamikaze fighter meant to destroy the opponent's few pokemon due to the recoils.
Why adamant nature?
With base Speed of 126, Talonflame easily outspeeds many pokemon in OU, including Greninja. Hence, a Jolly nature would be hindering the effectiveness of a Choice Banded Talonflame, which can potentially use the adamant's nature boost to cripple the enemies' pokemon further. However, there are Greninja users who tend to forego a minor part of the Sp.A / Attack and go for Speed natures and hence, that is why Jolly nature is viable too.

Tyranitar - Choice Scarf
252Attack/252Speed/4Hp
Ability : Sand Stream
Nature : Jolly / Adamant
- Crunch
- Stone Edge
- Earthquake
- Brick Break
A choice scarfed tyranitar protects itself by mainly few reasons. Firstly, With choice scarf, it's astounding speed can outspeed majority of the Pokemon in OU tier. Secondly, boasting high speed and aided by it's amazing Attack power, Tyranitar can do a revenge kill on a diversity of Pokemon. Also, a choice scarfed Tyranitar outspeeds a Gengar, which is one of the hardest check to it due to Focus Blast. However, a Mega Alakazam can send this choice scarfed Tyranitar straight back to it's Pokeball. This is a factor that disrupts Tyranitar's rampage.

Greninja - Choice Specs / Life Orb ( I don't really prefer Choice Specs as I consider Greninja to be a versatile killer )
252Sp.A/252Speed/4Sp.D
Ability : Protean
Nature : Timid
- Extrasensory
- Hydro Pump
- Dark Pulse / Spikes / Toxic Spikes
- Ice Beam
Being right now, even outspeeding Alakazam(Non-mega) and Gengar, one of the fastest Pokemons in OU - Greninja, with it's amazing Special Attack can basically OHKO with a super effective and a potential 2HKO with a 1x. Extrasensory provides protection against Fighting types. Dragons are a common sight, hence, I chose Ice beam to be in it's moveset to counter against Dragons. Hydro Pump is a must need to check against it's weaknesses which are usually common in OU. Dark Pulse is optional and can be switched to Spikes / Toxic Spikes using Life Orb Greninja due to it's common weaknesses being glass cannons. However, a Jolteon can easily cripple this guy easily due to Jolteon's reputation of being in one of the fastest tier for a long while.

Rotom-Wash - Assault Vest / Leftovers
232Hp/252Sp.A/26Def
Ability : Levitate
Nature : Modest
- Volt Switch
- Discharge / Will-O-Wisp
- Hydro pump
- Hidden Power Ice / Hex
Rotom-W has always been a good check and counter against various flying, ground, water, fire and rock types. With Will-O-Wisp and 26DEF in EVs, Rotom can take a hit from sweepers and lower it's attack with a burn ailment. Followed by Hex, which deals twice when a status ailment is applied, dealing a massive 130 damage onto the sweeper. It's basic moveset, Volt switch, has always been there to check for the opponent's Pokemons. Hydro pump, needless to say, is a must-have on rotom due to it being it's powerhouse with STAB damage. Discharge is an alternative for assault vests rotom, whom want to soak damage and still apply an ailment upon enemies. Hidden Power Ice is a good check against Dragons, Flying types, and the most commonly seen Dragonite and Garchomps.

Mawile - Mawilite
232Hp/220Attack/58Sp.D
Ability : Intimidate
Nature : Adamant
- Play Rough
- Sucker Punch / Crunch
- Swords Dance
- Iron Head
The moveset is pretty straight forward. A huge powered Mega Mawile with it's STAB Play rough can OHKO almost anything without HP/DEF investments. Sucker Punch is a good alternative from Crunch because of it's priority. Swords Dance can be used to predict a switch out, or a counter swords dance. Iron head is a check against Fairy types/Ice types and Rock Types. However, this little fella is pretty weak to any Fire/Ground pokemon that is faster than it and that is where intimidate comes on Physical Fire/Ground type moves. The 58EV investments in Special Defense and HP is to prevent it's super effectiveness ( hopefully ) to kill it in a hit, allowing Mega-Mawile to probably OHKO/Cripple it severely.

Aegislash - Weakness Policy
220Sp.A/252Hp/38Def
Ability : Stance Change
Nature : Quiet
- Flash Cannon
- Shadow Ball
- King's Shield
- Shadow Sneak
As an avid Aegislash user, I feel that this Pokemon is indeed a good one to use. A STAB shadow ball from this guy can pretty much leave your pokemon in smithereen. The investments in HP and DEF is to allow Aegislash to pretty much survive an earthquake or a super effective move against it, to allow the Weakness Policy to proc. King's shield is a must use to lower opponent's attack and to return to shield forme. Flash Cannon is another STAB to counter mainly against Fairies and do heavy damage to Pokemon that are oblivious to this terror's power. I chose shadow sneak to finish off low HP pokemon or to cripple Gengar/Alakazam ( with weakness policy active, it's a clean OHKO ).

Talonflame - Choice Band
252Attack/252Speed/4Hp
Ability : Gale Wings
Nature : Adamant ( I'll explain this later on ) / Jolly
- U-turn
- Brave Bird
- Flare Blitz
- Steel Wing
In this meta, where Fairies currently show huge dominance against the dethroned Dragons, I prefer Steel Wing to rid of them. U-turn serves as a great scouting tool with Choice Band, able to at least put out some damage before returning. Brave bird, as I tested in PSD, deals a OHKO on Sweepers and a potential 2HKO on Defensive walls. With the Gale Wings ability, this allows you to move first and deal a choice banded Brave Bird with STAB damage. Flare Blitz, aided by max EVs in Speed, gives Talonflame a huge advantage over it's type advantages, which are usually slow. However, despite it's great attacking prowess, you have to remember this guy is merely a kamikaze fighter meant to destroy the opponent's few pokemon due to the recoils.
Why adamant nature?
With base Speed of 126, Talonflame easily outspeeds many pokemon in OU, including Greninja. Hence, a Jolly nature would be hindering the effectiveness of a Choice Banded Talonflame, which can potentially use the adamant's nature boost to cripple the enemies' pokemon further. However, there are Greninja users who tend to forego a minor part of the Sp.A / Attack and go for Speed natures and hence, that is why Jolly nature is viable too.

Tyranitar - Choice Scarf
252Attack/252Speed/4Hp
Ability : Sand Stream
Nature : Jolly / Adamant
- Crunch
- Stone Edge
- Earthquake
- Brick Break
A choice scarfed tyranitar protects itself by mainly few reasons. Firstly, With choice scarf, it's astounding speed can outspeed majority of the Pokemon in OU tier. Secondly, boasting high speed and aided by it's amazing Attack power, Tyranitar can do a revenge kill on a diversity of Pokemon. Also, a choice scarfed Tyranitar outspeeds a Gengar, which is one of the hardest check to it due to Focus Blast. However, a Mega Alakazam can send this choice scarfed Tyranitar straight back to it's Pokeball. This is a factor that disrupts Tyranitar's rampage.

Greninja - Choice Specs / Life Orb ( I don't really prefer Choice Specs as I consider Greninja to be a versatile killer )
252Sp.A/252Speed/4Sp.D
Ability : Protean
Nature : Timid
- Extrasensory
- Hydro Pump
- Dark Pulse / Spikes / Toxic Spikes
- Ice Beam
Being right now, even outspeeding Alakazam(Non-mega) and Gengar, one of the fastest Pokemons in OU - Greninja, with it's amazing Special Attack can basically OHKO with a super effective and a potential 2HKO with a 1x. Extrasensory provides protection against Fighting types. Dragons are a common sight, hence, I chose Ice beam to be in it's moveset to counter against Dragons. Hydro Pump is a must need to check against it's weaknesses which are usually common in OU. Dark Pulse is optional and can be switched to Spikes / Toxic Spikes using Life Orb Greninja due to it's common weaknesses being glass cannons. However, a Jolteon can easily cripple this guy easily due to Jolteon's reputation of being in one of the fastest tier for a long while.

Rotom-Wash - Assault Vest / Leftovers
232Hp/252Sp.A/26Def
Ability : Levitate
Nature : Modest
- Volt Switch
- Discharge / Will-O-Wisp
- Hydro pump
- Hidden Power Ice / Hex
Rotom-W has always been a good check and counter against various flying, ground, water, fire and rock types. With Will-O-Wisp and 26DEF in EVs, Rotom can take a hit from sweepers and lower it's attack with a burn ailment. Followed by Hex, which deals twice when a status ailment is applied, dealing a massive 130 damage onto the sweeper. It's basic moveset, Volt switch, has always been there to check for the opponent's Pokemons. Hydro pump, needless to say, is a must-have on rotom due to it being it's powerhouse with STAB damage. Discharge is an alternative for assault vests rotom, whom want to soak damage and still apply an ailment upon enemies. Hidden Power Ice is a good check against Dragons, Flying types, and the most commonly seen Dragonite and Garchomps.

Mawile - Mawilite
232Hp/220Attack/58Sp.D
Ability : Intimidate
Nature : Adamant
- Play Rough
- Sucker Punch / Crunch
- Swords Dance
- Iron Head
The moveset is pretty straight forward. A huge powered Mega Mawile with it's STAB Play rough can OHKO almost anything without HP/DEF investments. Sucker Punch is a good alternative from Crunch because of it's priority. Swords Dance can be used to predict a switch out, or a counter swords dance. Iron head is a check against Fairy types/Ice types and Rock Types. However, this little fella is pretty weak to any Fire/Ground pokemon that is faster than it and that is where intimidate comes on Physical Fire/Ground type moves. The 58EV investments in Special Defense and HP is to prevent it's super effectiveness ( hopefully ) to kill it in a hit, allowing Mega-Mawile to probably OHKO/Cripple it severely.

Aegislash - Weakness Policy
220Sp.A/252Hp/38Def
Ability : Stance Change
Nature : Quiet
- Flash Cannon
- Shadow Ball
- King's Shield
- Shadow Sneak
As an avid Aegislash user, I feel that this Pokemon is indeed a good one to use. A STAB shadow ball from this guy can pretty much leave your pokemon in smithereen. The investments in HP and DEF is to allow Aegislash to pretty much survive an earthquake or a super effective move against it, to allow the Weakness Policy to proc. King's shield is a must use to lower opponent's attack and to return to shield forme. Flash Cannon is another STAB to counter mainly against Fairies and do heavy damage to Pokemon that are oblivious to this terror's power. I chose shadow sneak to finish off low HP pokemon or to cripple Gengar/Alakazam ( with weakness policy active, it's a clean OHKO ).