The Davy knot is the creation of Davy Wotton, a Welshman relocated to Flippin, Arkansas, who has been fly fishing since the 1960s. Many anglers love the knot because it’s quick to tie and is quite small. These videos from Tightline Productions show you two versions, which you can try on the water. I know several anglers who simply swear by the Davy knot and use it for all dry flies and nymphs.
For more information on Davy himself, check out his elaborate website.