For fishing subsurface I like to use "Fur-buggers". See the fly of the week for the "Woolly Fur-bugger". Size 10 works well. I also like a version that I often tie smaller (size 12) called a "Hare and Herl Bugger".

http://www.flyanglersonline.com/flytyin ... 6fotw.html

http://www.fishingwithflies.com/HareandHerlBugger.html