Veevus 12/0 Thread
Veevus 12/0 is a very thin fly tying thread that is said to be twice the strength of nylon threads of similar size. It ties a bit more round than an Ultra Thread or Danville, but this Veevus 12/0 is pretty dang nice on smaller flies and has the strength to make it quite versatile for lots of tying applications. Veevus 12/0 is also great for finishing flies when you want a tiny little thread head.