For me it's borders... I have so many strips that I cut and some that I've actually sewn down and taken off again. I prefer to cut length wise so they are usually 3 yards long.
For one of my recent donation projects I set out with the idea of using a particular piece for the back. Only I decided the top needs another 4" of border all around and that's too big for the fabric. And the second choice. I found a 3rd choice that was large enough but I just didn't like it.
When I dove into my "pieces big enough for backs" to bring a selection for one of my Tuesday group members (she chose to keep looking) I found two pieces I had forgotten about, either of which would make a great back. And then one of the other Tuesday ladies brought fabric to share which included a perfect flannel for the back. Now I have 3 choices! Which means I have 2 more quilts to make...