My "always handy" items:
Thread snips - 3 of them. One at the machine, one at the ironing board, one on my cutting table. All three are different. A crane, ginghers, and a tweezer type.
4 1/2 square ruler - use it for squaring up, finding a straight edge, measuring - lots of stuff and it's handy.
Regular lead pencil - I'm always jotting notes and doing math.
then the usual as needed items - rotary cutter, cutting mat, iron, pins, and various rulers.