In my previous blog post I mentioned a few flies I'd received from my friend from Pennsylvannia, Fred Bridge. I've posted a closeup photo and the tying sequence for one of these flies, the Wonder Bug.
If I could pick only two materials with which to tie nymphs, I would pick (1) lead and (2) peacock herl. Add some hackle and you've got the Wonderbug.
Check it out here: http://www.fishingwithflies.com/WonderBug.htm