One of the challenges in Rune Factory 2, long after you have completed the 'story' is to complete your Shipping List. Although your character can have two Refrigerators and two Shelves, the fact that items can be anything from Level 1 to Level 10 make it almost impossible to store everything you need to forge all weapons and accessories and make Cooked Dishes and Medicines. The random quality of mining and Inquisitive Waltz treasure hunts almost guarantees that you will fill your Rucksack far too quickly with items of the same type but different quality levels.
I therefore began to designate some of the items by use in order to be able to clear out my Rucksack quickly without wasting any potentially useful ingredients.
For example, in the early days of the 2nd Generation, I found that I always needed more Silver as many low-level forging and accessory projects require Silver. Now, later in the game, I find that I collect too much Silver and never enough Gold.
I therefore began to hunt for uses for the Silver...
A quick study of Recipe Lists reminded me that upgrades for all Elemental Rings and Pendants use Silver. It is better to use the Silver to upgrade all Elemental Rings and Pendants to Level 10 than to ship the Silver or give it to my father. It is not for profit's sake but for the sake of increasing Skill Levels.
Although a few projects require Scrap Iron, for the most part it IS a fairly useless valueless item and therefore I give all Scrap Iron to my father, who often reciprocates with a gift of ICE CREAM. A Level 1 ICE CREAM has a shipping value of 6780G. Although you need to give him two gifts to obtain one after the very first exchange, it is well worth the effort. ICE CREAM may be the most valuable gift he gives, but the others certainly are worth more than SCRAP IRON.
This little gift-giving option in Rune Factory 2 reminds me of an essential point in the philosophy of Harvest Moon, to the effect that no item in this universe truly is useless. In how many Harvest Moon games has a common WEED been an essential ingredient in a Recipe? The fabled ELLI LEAVES are made from Failed Dishes/Burnt Dishes...