Dials: Dials can only be obtained after visiting a sky island. This rule does not apply to Skypiens and Harpies.
Custom Weapons: Copies of custom weapons can only be bought if the creator specifies there are more than one in existence in the creation thread.
Stat Boost: Only weapons in the O Wazamono and Saijo O Wazamono can give the user a stat boost. They give 10% and 20% respectively.
Stat Boosters: Items that give the user a temporary stat boost are allowed, however these will be expensive and short lived (1-2 posts).
Only one character can start with a devil fruit weapon: . Of all your devil fruit weapons, no single character possessing them can have more than one Mythical or Ancient zoan, or more than one logia. You may have one, logia and one M/A zoan, but not both a Mythical and an Ancient zoan. Ancient zoans are rare, logias rarer, and Mythical zoans are extremely rare, and that is why we limit this and we can't have you taking all our fun toys. Keep in mind that your devil fruit weapon may be using the fruit someone else wants to use. It's still first come, first serve, but in my personal opinion characters are far more important than weapons, so you may be screwing someone over and wasting their hard work.