I was just reading about different stitches and needles to use for embroidery. Most stitches can be created by using regular embroidery needles. However, according to Mary Corbet, using the right needle is the key to making perfect French Knots and Bullion Knots. On her blog she says that using a straw needle or milliner's needle is the perfect tool for making these stitches. If you have any of these on hand, you will notice that the shape of the straw needle is different from other needles. There is no bulge around the eye therefore making the shaft and the eye the same size the full extent of the needle. So when you pull the needle through a series of thread wraps, it goes through easily without the eye getting caught up in the wraps. Check out the rest of her article and see a picture of straw needles.
A couple of years ago, I did a three year hand embroidery course. Over the months, one of the class members kept saying that she only joined the class to learn how to make French Knots. This got to be a bit of a class chuckle. After the course was finally finished, we had an exhibit of all our work. We called it, "All I ever wanted to learn was French Knots". In fact most of the ladies who took this course still meet every Thursday evening to stitch, thus the name FETE (friends every Thursday evening).
Tanja Berlin has a lot of information on her site about embroidery needles.
Check out Victorian Embroidery and Crafts for information of selecting the right needle for your project.