If you are facing someone who is Japanese, you should know their own standard rule.
Their rule is based on the battle tower(battle subway) rule.
The interesting point is that their rule is lot different than ours, and they don't specifically ban Garchomp and Wubbuffet.
Overpowered(uber legend) Pokemons
-Mewtwo
-Ho-Oh
-Lugia
-Kyogre
-Groudon
-Rayqueza
-Dialga
-Palkia
-Giratina
-Arceus
-Reshiram
-Zekrom
Event Pokemon
-Mew
-Celebi
-Jirachi
-Deoxys
-Phione
-Manaphy
-Latios & Latias (with Soul Dew)
-Darkrai
-Shaymin
-Victini
Standard Rule Option A
Any pokemons that have total base stats over 580 are not allowed (excluding Slaking)
Unable to use
Pokemons with base stats total 600
-Dragonite
-Tyranitar
-Salamance
-Metagross
-Garchomp
-Hydreigon
3 Legends
-Kanto 3 Legends (Moltres, Zapdos, Articuno)
-Johto 3 Legends (Raikou, Entei, Suicune)
-Houen 3 Legends (Regirock, Regice, Registeel)
-Sinnoh 3 Legends (Uxie, Mesprit, Azelf)
-Unova 3 Legends (Cobalion, Terrakion, Virizion)
Other Legends
Houen
-Latios
-Latias
Sinnoh
-Heatran
-Regigigas
-Cresselia
Unova
-Tornadus
-Thundurus
Plus Uber Legend Pokemons and Event Pokemons are not allowed.
Standard Rule Option B
All the pokemons are allowed to use plus the event Pokemons except Uber Legend Pokemons.
No Restriction Option C
All Pokemons are allowed.
In Japan no matter which rule you play, you must follow below:
Item Clause
A Clause heavily enforced by all official Nintendo tournaments. Players are not allowed to have two or more of the same item on any of their Pokemon.
Species Clause
No two Pokemon of the same species may be used on the same team.
Self KO Clause
If both players have only one Pokemon remaining in battle moves that KO the user, such as Explosion or Destiny Bond, are not allowed. If a player uses a move that causes recoil damage such as Flare Blitz ends the game in both Pokemon fainting, the player that attacked last is announced the winner. If a player's pokemon has a life orb and it faints the pokemon in the end, then a player that attacked last is announced the winner.
Sleep Clause
The players may not put more than one Pokemon on the opponent's side to Sleep. The move Rest and Metronome are not affected by this clause.
Also, this clause is not affected if one is forced to use a sleep move under the restriction by the move Encore, or if a pokemon cannot use any other moves because it has any Choice items because foe used a move Trick.
This clause is also not affected if one uses Magic Coat, Mirror Move, or Copycat to make foe sleep.
This clause is affected if one uses a move Sleep Talk or Assist.
Japan does not have Evasion, Freeze, One-Hit KO, and Hax Clauses because Japanese think they are part of strategies.
In Japan, One-Hit KO is regarded as the part of strategy as to destroy Pokemons with high durability.
Rapidash's Hypnosis and Horn Drill combo is one of the famous One-Hit KO strategy among Japanese Pokemon Trainers.
You must choose from different single battle options:
66 battle
33 battle
6350 battle (You show 6 Pokemons and choose 3)
Why Garchomp and Wobbuffet are not banned in Japan?
Although Garchomp (Yachechomp, or Scarfchomp) is also used widely in Japan, it is not banned because many have managed to find the counter-measure against it such as increase in usage of Pokemons with high defense. Also, movements or ability that decrease Garchomp's its attack power such as intimidate help to defeat Garchomp.
Will-o-wisp and reflect especially are greatly effective against Garchomp.
Famous Garchomp killer pokemons are
Gyarados, Mamoswine, Weavile, and etc.
Wobbuffet is banned in US because Wobbuffet's ability, Shadow Tag, prevents switch-outs and draws battles into unneccessary lengths of time.
However, in Japan it is not banned because people have found the counter-measure.
Effective Movements against Wobbuffet
U-turn, Volt Switch, Baton Pass, Skill Swap, and ability Trace
Taunt, Encore, and etc.
What should you do if you don't have these movements above?
Try increase your stats using Sword Dance or any other movements that help to increase your stats so that you can defeat Wobbuffet with One Hit.
Movements such as Toxic, Thunder Wave, or Will-o-wisp or any other Status move may help.
The point is, don't just carry a Pokemon that only has battle moves.
The Standard Rule in Japan is much easier to remember and formalized than our rule.
We have OU, UU, and whatever however in Japan they have already created the categories according to their base stats so that everytime new pokemon appears they don't have to think which pokemon is uber or which is not.
The cons with Japanese standard rule is that there is a huge difference between beginners and advanced players, which is why all the people you see in Random wi-fi battle are Japanese because beginners don't go to wi-fi battle.
I think some of our standard rules should be changed because we have way too many clauses.
Famous Japanese Pokemon websites
http://www14.atwiki.jp/bwpokekousatsu/ Pokemon 5th Generation Battle Wiki
-greatly focuses on battle against people. It shows the details of every Pokemon regarding to battle such as moves, abilities, EVs, and IVs. High level of Japanese is recommended.
http://www18.atwiki.jp/dppokekousatsu/ Pokemon 4th Generation Battle Wiki
Their rule is based on the battle tower(battle subway) rule.
The interesting point is that their rule is lot different than ours, and they don't specifically ban Garchomp and Wubbuffet.
Overpowered(uber legend) Pokemons
-Mewtwo
-Ho-Oh
-Lugia
-Kyogre
-Groudon
-Rayqueza
-Dialga
-Palkia
-Giratina
-Arceus
-Reshiram
-Zekrom
Event Pokemon
-Mew
-Celebi
-Jirachi
-Deoxys
-Phione
-Manaphy
-Latios & Latias (with Soul Dew)
-Darkrai
-Shaymin
-Victini
Standard Rule Option A
Any pokemons that have total base stats over 580 are not allowed (excluding Slaking)
Unable to use
Pokemons with base stats total 600
-Dragonite
-Tyranitar
-Salamance
-Metagross
-Garchomp
-Hydreigon
3 Legends
-Kanto 3 Legends (Moltres, Zapdos, Articuno)
-Johto 3 Legends (Raikou, Entei, Suicune)
-Houen 3 Legends (Regirock, Regice, Registeel)
-Sinnoh 3 Legends (Uxie, Mesprit, Azelf)
-Unova 3 Legends (Cobalion, Terrakion, Virizion)
Other Legends
Houen
-Latios
-Latias
Sinnoh
-Heatran
-Regigigas
-Cresselia
Unova
-Tornadus
-Thundurus
Plus Uber Legend Pokemons and Event Pokemons are not allowed.
Standard Rule Option B
All the pokemons are allowed to use plus the event Pokemons except Uber Legend Pokemons.
No Restriction Option C
All Pokemons are allowed.
In Japan no matter which rule you play, you must follow below:
Item Clause
A Clause heavily enforced by all official Nintendo tournaments. Players are not allowed to have two or more of the same item on any of their Pokemon.
Species Clause
No two Pokemon of the same species may be used on the same team.
Self KO Clause
If both players have only one Pokemon remaining in battle moves that KO the user, such as Explosion or Destiny Bond, are not allowed. If a player uses a move that causes recoil damage such as Flare Blitz ends the game in both Pokemon fainting, the player that attacked last is announced the winner. If a player's pokemon has a life orb and it faints the pokemon in the end, then a player that attacked last is announced the winner.
Sleep Clause
The players may not put more than one Pokemon on the opponent's side to Sleep. The move Rest and Metronome are not affected by this clause.
Also, this clause is not affected if one is forced to use a sleep move under the restriction by the move Encore, or if a pokemon cannot use any other moves because it has any Choice items because foe used a move Trick.
This clause is also not affected if one uses Magic Coat, Mirror Move, or Copycat to make foe sleep.
This clause is affected if one uses a move Sleep Talk or Assist.
Japan does not have Evasion, Freeze, One-Hit KO, and Hax Clauses because Japanese think they are part of strategies.
In Japan, One-Hit KO is regarded as the part of strategy as to destroy Pokemons with high durability.
Rapidash's Hypnosis and Horn Drill combo is one of the famous One-Hit KO strategy among Japanese Pokemon Trainers.
You must choose from different single battle options:
66 battle
33 battle
6350 battle (You show 6 Pokemons and choose 3)
Why Garchomp and Wobbuffet are not banned in Japan?
Although Garchomp (Yachechomp, or Scarfchomp) is also used widely in Japan, it is not banned because many have managed to find the counter-measure against it such as increase in usage of Pokemons with high defense. Also, movements or ability that decrease Garchomp's its attack power such as intimidate help to defeat Garchomp.
Will-o-wisp and reflect especially are greatly effective against Garchomp.
Famous Garchomp killer pokemons are
Gyarados, Mamoswine, Weavile, and etc.
Wobbuffet is banned in US because Wobbuffet's ability, Shadow Tag, prevents switch-outs and draws battles into unneccessary lengths of time.
However, in Japan it is not banned because people have found the counter-measure.
Effective Movements against Wobbuffet
U-turn, Volt Switch, Baton Pass, Skill Swap, and ability Trace
Taunt, Encore, and etc.
What should you do if you don't have these movements above?
Try increase your stats using Sword Dance or any other movements that help to increase your stats so that you can defeat Wobbuffet with One Hit.
Movements such as Toxic, Thunder Wave, or Will-o-wisp or any other Status move may help.
The point is, don't just carry a Pokemon that only has battle moves.
The Standard Rule in Japan is much easier to remember and formalized than our rule.
We have OU, UU, and whatever however in Japan they have already created the categories according to their base stats so that everytime new pokemon appears they don't have to think which pokemon is uber or which is not.
The cons with Japanese standard rule is that there is a huge difference between beginners and advanced players, which is why all the people you see in Random wi-fi battle are Japanese because beginners don't go to wi-fi battle.
I think some of our standard rules should be changed because we have way too many clauses.
Famous Japanese Pokemon websites
http://www14.atwiki.jp/bwpokekousatsu/ Pokemon 5th Generation Battle Wiki
-greatly focuses on battle against people. It shows the details of every Pokemon regarding to battle such as moves, abilities, EVs, and IVs. High level of Japanese is recommended.
http://www18.atwiki.jp/dppokekousatsu/ Pokemon 4th Generation Battle Wiki