I do almost everything with Superior Threads Bottom Line - it's a 60wt, so very thin.
If it's machine quilting and I want it to show abit, I use Superior Threads' King Tut instead of Bottom Line
If I want use cotton in piecing, hand or machine, my first choice is Aurifil 50 wt, 2nd choice Masterpiece (also a Superior Thread product).
NEVER use hand quilting thread in your machine