Emergency Parts Kit

OK, I am bringing my wife again this year. During the conference she visits quilt shops in the area looking for deals during the day, so I have to keep up with her with regards to spending. I am looking to stock up on some parts, especially since my machine is out of warranty. That being said, what spare parts should I have on hand? Maybe if this list is too extensive, a couple of categories such as Must Have, Should have? I know this has been done in the past, but not sure if things have changed. BTW, I have a "C" machine so may want to note if something is only for 1 type of machine.