pflum1

A seam ripper is a must have.
Needle threader, the nice kind.
wash away thread and fusible thread.

deltaquilter

John James Gold 'n Glide needles. I like size 10 or 11--a long thin needle that goes through fabric like butter. Love them.

dlux

These are all great ideas, one thing I didn't see mentioned is a magnetic wand for picking up spilled pins or a needle which has flipped out of sight. I have several, one in each "to go" sewing box, and one beside my sewing machine. There is also one on my cutting table. I keep another one handy for the grandkids to goof around with when they stop by.
There are some pretty ones at Hobby Lobby but the strictly functional ones can be found in any auto parts dept.

Steady Stiching

Lately my go to tool has been a bone folder, great for birthing anything, spritz seam with water, zip the bone folder along the seam and it lays flat with no effort at all. Love it!
I should mention that I have been making a lot of stuffed toys, handbags and xmas stockings...lots of birthing.

Michellesews

Hemostats, no doubt. I am constantly using them to pull thread from the machine or take picked threads from a quilt...they grip like crazy and sometimes, there is no substitute for grip...tweezers just don't cut it.

BarbM32

All the above sound great but I love my 4" square ruler as well and the 6" square but not sure how much 6" costs. Every so often I lose my little ruler so now have 2 of them. The lost one will eventually show up so now I do not have to spend time hunting for it when I am doing the small blocks. I like to check my sewen squares and there are times when it does not look right before sewing and no trouble to check. The kingquilt I am working on is made up entirely of
2 1/2 inch blocks and 4 1/2 inch blocks. The small ruler has been a life saver after I started using it regularly.

judi wess

I love the blue rinsable markers, can never have too many of these. Love Thread Heaven, Sew Easy and my Dritze sewing and knitting guage, it has a sliding thing in the center that lets you keep your measurement and slots for marking accurately.

Sierra

I love the purple thang, but my first thought was a magnetic bowl. It is still unusual and is so wonderful for pins!

Sierra

It is a small stick like thing about the size of a large crochet hook but very different. You might describe it as a finger saver. You can use it to hold down a seam allowance as you sew over it, adjust precisely where your seam is going to be when sewing.... oh, lots of things. I quilt on my regular sewing machine and it really comes in handy then. The shape of it was obviously designed by a quilter. You can use it to push out corners until they are perfect. They are addictive. great and very inexpensive.

SunlitenSmiles

purple thang or a porkeypine (sp?) quill wraped in a fat quarter