No zakaah is required of a person for what he owns of weapons, animals, clothing and the like, unless it is for trade. The evidence for that is the words of the Prophet (peace and blessings of Allaah be upon him): “No zakaah is due from the Muslim for his slave or his horse.” Narrated by Muslim (982).
Al-Nawawi (may Allaah have mercy on him) said: This hadeeth is the basis of the principle that no zakaah is due on one’s own property, and no zakaah is due on horses and slaves if they are not for trade. End quote from Sharh Muslim.
One's own wealth means that which a person keeps to make use of and benefit from, not for purposes of trade. On this basis, no zakaah is due on the dagger and revolver, unless they are prepared for sale, in which case zakaah is due on them. See also the answer to question no. 65515 for information on how to pay zakaah on trade goods.
It should be noted that the dagger may be made of silver or plated with gold. If the gold or silver in it reaches the nisaab (minimum threshold) then zakaah is due on it; or if it is less than the nisaab but the owner has other gold or silver that reaches the nisaab when put together with it, then zakaah is also due on it.
But if the gold or silver in it is less than the nisaab and the owner has no other gold or silver, then no zakaah is due on it.
The scholars of the Standing Committee were asked: is a personal weapon such as a rifle, revolver or sword subject to zakaah, and how should it be paid?
No zakaah is due on that because it is not prepared for trade. But if there is any gold on the sword etc that reaches the nisaab by itself or when added to other gold that he owns, then he must pay zakaah, according to the more correct of the two scholarly opinions, as is the case with jewellery. End quote.
Fataawa al-Lajnah al-Daa’imah (9/276)
And Allaah knows best.