I love my Bloc Lock ruler and use it all the time whenever I need to square up any HST.
Also love my Deb Tucker wing trimmer for my flying geese.
I hesitated on buying these for over a year. But when a friend of mine finally purchased, I went to her house to try and purchased it online that day.
My EQ7 software was another item I hesitated on buying. Now I don't know how I managed without it.
Someone mentioned those sharp tweezers that come with the curved presure foot. Love that, too, and use it all the time.