Besides stitch markers of course, I have a Must Have in my knitting bag at all times. It is a Silvalume Handi Tool.
If you aren't familiar with it, it is a small tool about 4 inches long with a crochet hook on one end and a knitting needle on the other! It is brilliant! It is perfect to pick up dropped stitches and you can use it as a cable needle.
I make sure each of my notions pouches has one in it. Plus they are inexpensive! I have an Amazon link for you if you want one or two!