How can I craft the Golden Wrench?

You can no longer craft the Golden Wrench (or rather, receive while crafting other things), and the 100 people that won it and another who bid on it are the only ones who ever will as it is not tradable.

From the original 100 & 1, at least 19 have been destroyed, 14 of which net $31,000 for Child's Play, another raised $530 for the same charity, and one more provided 10,200 TWD (~$344) for a 2011 Sendai earthquake & tsunami charity. Why people donated so much money to have someone destroy a virtual item is beyond me, but I'm not going to argue with results.

It seems to be any item. If you already have a token, it only takes one other weapon to complete the craft, so this is the cheapest option. This produces no scrap metal, however.

There may have recently been changes to the drop algorithm that was in use just today, since it seems that several users have figured it out. That has yet to be seen.