In Patapon 3, most weapons can be gained by normal means of playing. Some weapons, however, are simply "disabled" and can not be gained at all, without hacking the game of course. There's currently 7 weapons that can not be gained by chest, and only 1 of them are given to you by the game.
A spear that is one of the mystery weapons. It is not known why it's not obtainable. Has high damage and freezing power.
Gardsormr Ice Claw
Along with the Trident and Deathsoul, it remains a mystery why we can't obtain these. These claws have freezing powers and with two of them you can throw icy rocks
Bengal Tiger Claws
It is unknown as to why this is unobtainable. Reduces damage taken from stab, slash and strike attacks.
Kaisak Ultimate Claw
There are 2 main reasons why these claws are unobtainable. The first one is because Dark Heroes can not get Pink Jewled Chests. (or purple, what ever your preference for the rare DOJ chest is). Since Ultimates only are obtained in these chests, there's no way for a dark hero to get them. The second reason is because, even though you can get ultimates in Uber Hero mode, you can only gain equipment that corresponds to a usable class. For example; In Dark Hero, shoulders are not able to be gain in chest because Tondenga is not a playable class (by normal means) in Dark Hero. Due to this, in Uber Hero any Claw and Scythe related weapon is not able to be obtained. This means you can not gain the ultimate scythe or claw and transfer it to dark hero. One way to do it is hacking in Ragewolf or Ravenous in Uber Hero mode.
This, just like the Poseidon's Trident, is unobtainable but there's no answer to why. It has sleep and poison powers.
Great Mighty Scythe
Technically, this weapons is able to be obtained, but only if you make a new Dark Hero save. When you do, they game will automatically "gift" it into your armoury. Besides that, There is no other way to get it. This is most likly because S.U gear is unobtainble in Dark Hero. Has Light-attack element and high critical ratio.
Deathmoon Ultimate Scythe
The same reasons for the ultimates claws.