Responding to another thread got me thinking about things in our workbox that we wouldn't do without, and apologies if the subject has been raised in the past.
First and foremost I reckon has to be good scissors. We have some Fiskars spring-loaded, large and small, and they're excellent.
Extending magnet, for retrieving dropped pins.
A cheapo combined needle threader and seam ripper - I seem forever to be reaching for the seam ripper, and my fat fingers always struggle to thread a needle. Got three or four always in reserve for when the threader wire parts!
A flexible wire bodkin about 6" long.
Several scalpels of various shapes.
Oh, and my clip-on magnifying glasses! :-)
Needless to say, there are lots of things we need and use, but those are things I wouldn't want to be without.