Many trout fishermen love the Perfection loop for a loop to loop connection from the leader to the fly line. I like this knot because it is extremely strong. In fact, many others use this knot to tie a fly, lure, hook or jig to the end of the line. It is an extremely strong loop knot.
My one issue with this knot is not concerning it's strength but rather with the way the tag end sticks out perpendicular to the line. This causes some problems with it going through the rod guides and can even result in lost fish when fishing with light tippets.
I still use the knot often, but really only on my trout leaders. I prefer the Surgeons loop (Click here for full instructions on the Surgeon's loop) for my saltwater leaders for the same type of loop to loop connection.
Here is how to tie the Perfection Loop. If the video does not display for you, please click here