After washing out and getting 15 stitches on my right shin, I decided it was time for some knee/shin guards. I picked these up, because they were super cheap and offered good protection: Fox Launch Sport Knee Guard ($28). I also recently got the Fox Launch Pro D30 Elbow Guards ($100). I live and ride in Northwest Arkansas, and we have some pretty rocky trails here.
The knee guards do the job, but tend to slip down. I’m much happier with the elbow guards, which stay in place better and look better. Both are comfortable though, and I don’t notice them much—especially the elbow guards. No crashes in either yet!