Optional Clauses
Item Clause: By far the most common non-standard rule, item clause states that each Pokemon on the team must be holding a different item from one another. So no double leftovers or focus sash. Items that do the same thing but aren't the same however are allowed. An example of this: Leftovers and Black Sludge.
Luck "Hax" Item Clause: In online competitive play, the term "Hax" refers to when something unlucky occurs to you. Most of the time this is that 30% chance to freeze from a Ice beam, or something of that nature and it's just the way the game goes. Although, when it comes to hold items that have small chance of completely turning the game around just out of sheer chance, it's deemed rather frustrating and very similar to the OHKO Clause. For this reason, when this clause is in effect, that means the following items are banned from use: Brightpowder, Quick Claw, Razor Fang, Focus Band and King's Rock.
Legendary Clause: When this is in play, all legendaries, Ubers and non-Ubers alike, are banned from use.
Trios Clause: This clause states that only Trios legendaries may be used. The trios are the legendary birds (Articuno, Zapdos and Moltres), legendary dogs (Entei, Suicune and Raikou), Legendary Golems (Regirock, Registeel and Regice) and Mirage Trio (Uxie, Mesprit and Azelf).
Explosion/Selfdestruct Clause: Only one Pokemon per team can use either Explosion or Selfdestruct.
Switch Clause (X switches): Also known as the
"Switch b***h" Clause, this rule pretty much presets what the invoker feels is an acceptable amount of switches any player may do back-to-back. This amount is dictated in place of the X.
Big 5 Clause: Only one of the following Pokemon may be used per team: Dragonite, Tyranitar, Salamence, Metagross or Garchomp.
Skarm/Cress/Bliss Clause: Only one of the following Pokemon may be used per team: Skarmory, Blissey or Cresselia
Paralysis Clause: This clause states that you may not paralyze more than one of your opponent's Pokemon at a time through use of status moves (Thunderwave, Stun Spore and Glare). As there tends to be mixed feelings concerning how this clause operates, when in effect, it is generally best to ask it's invoker's opinion on whether or not attacking moves and/or abilities (ex: Static) also apply to this clause.
Poison Clause: Definitely the most uncommon of clauses, the poison clause states that you cannot poison more than one of your opponents through use of status moves (Poison Gas, PoisonPowder, Toxic Spikes and Toxic). Similar to the
Paralysis Clause, it is generally best to ask it's invoker's opinion on whether or not attacking moves and/or abilities (ex: Poison Point) also apply or not.
Freeze Clause: Although very absurd by clause standards, as there is no move yet in existence that automatically freezes an opponent, this clause generally states that you may not freeze more than one of your opponent's Pokemon at a single time. Generally tied in with the Sleep Clause (see Combo Clause section), I can see it's uses there, but alone, it really makes little or no sense to forfeit via use of hax (see above for meaning of "hax").