The only weapons that use monster bones to make are the bone sword GS, Bone LS, and the Agito GS. If your asking about Elder Dragon Bones, there are no weapons that ONLY need these, but there are some weapons that require the use of elder dragon bones. In the farm, there is a cave near the big tree by the bug patches. In the cave, a felyne will ask you if you want to make a type of pickaxe. you need 2 elder dragon bones for this, and then you can mine from the big black sword. The materials you will get will be dark stones and dark pieces. You cannot actually get that sword, but the closest thing to it is the black sword GS, which becomes available after getting the dark materials, along with other black weapons.(NOTE: the upgrades for the black weapons need FATALIS materials, so don't get them if you don't have the fatalis quests[all three of them]). If you have any further questions or you did not find what you were looking for, feel free to email me any questions about MHF2 at Monsterhunter.firstname.lastname@example.org Enjoy.