For me, it's the walking foot on my sewing machine. I don't think I do all the stitch in the ditch without one. I love it.
I do have another one, I also love embroidery machine. Besides the embroidery quilts that I do, I love how I'm able to do machine applique wiht it. I have always love applique quilt but can't seem to get it done right. With the embroidery machine, I can make it look so professional.
So, tell me what is your most important quilting tool.