I strive to be minimalist with my fly tying, these days, so I rarely play around with new materials. There are two notable things that I have been using a lot, over the last couple of years, to good effect.
1. Grizzly hen hackle. I use this on any subsurface fly that calls for hackle; wooly buggers, soft hackle nymphs, etc. It seems to fish better than saddle hackle, CDC, partridge and all the other things I used in the past. I often trim off one side of the feather, to make it more sparse. A brown wooly bugger, with grizzly hen hackle, is my "one" fly; I don't think I have ever not caught a fish on this fly. I avoid using it, unless I am desperate, because it feels like cheating now.
2. Custom rabbit dubbing blend, consisting of equal parts black, white, brown and olive. I mostly tight line nymphs, which means I need every pattern in 2-3 different weights. If I had 2-3 weights and 2-3 colors of every fly, I would never leave the vise and go fishing. Color is far less important than weight, so I've tried to find ways to tie every fly in just one color. Mixing up my own blend, containing all the common colors, seems to work for me.