"Thread throw up"/bobbin barf/thread nest/#%#*%(&*^)*&
That has to be number one but I am really irritated when:
I break needles
the blocks don't line up perfectly
I'm just shy of the amount of material I need for a project
I have to bump one project for another priority one and have a hard time getting back to the first one
and when I have to do real laundry before fun fabric laundry.