Aragorn held off four Nazgul on Weathertop with a torch, and because of that, they could not get the Ring from Frodo. That was the one thing the Nazgul were sent to do, the most important task in all Middle Earth, and the Ring was right there just a few feet away, but they just couldn't get past the waving torch and had to leave. No doubt, Sauron must have soon learned of this and instituted a counter-torch training program.
