Let's try this again. You could just drop the hat to make room for the glass shards, but you have a better idea. You try to pick up the glass shards with violent intent and unlock a "Weapon" slot. Congratulations! Not only does this allow you to carry a little more, you can now use the glass shards (or another equipped weapon) to do a basic Attack. Weild this power carefully, or you could end up getting cut yourself. It IS literally just a handful of glass.