I love to collect thread.... mostly in the basic colors. My favorite thread is Aurifil - it is very thin but strong and so a full bobbin lasts for a long time. It is expensive - usually around 9.00 a spool but it is worth it. I once had to have some blue thread for some applique on a towel... it was Sunday and had to go to Wal-Mart. All it did was broke.... I had to wait till Monday and go to my LQS to get good thread to finish the project! So now I only buy at my LQS.
My LQS only carries Metler and Gutermann so I always buy the basic colors of Aurifil when I find it!
I have tried a black King Tut and love that for machine blanket stitch applique.