I almost always use Aurifil. It is the best "normal" weight thread I've ever used, and I've used a lot of thread. I often use King Tut quilting thread in the top and Aurifil in the bottom for fmq. I normally work with a neutral color, so when a specific color is required (top stitching) I use a C&C from a large stash that I am trying to use up. I'll be glad when the C&C is gone.
Someone asked about using embroidery thread. All the emb thread I have for my machine is rayon or poly. I tried it once for piecing, but it melted when I ironed the seam, Fortunately I saw it before I sandwiched the quilt so I was able to resew it. Lesson learned: Always use thread that will take the same heat as the fabric. I do use emb thread for decorative stitching on quilts.