Many years ago I acquired a rare and unique tool from a colleague and it has become a valued treasure of mine. It's a keyhole buttonhole cutter. There's a blade on one side and the other side has a carousel of various keyhole sizes. You just twist to the right size keyhole, align over your fabric where you have sewn a keyhole buttonhole and squeeze to cut! This yields such a professional result! They don't make these anymore so now you can see why it would be a treasure to me.