The loop knot that Kelly linked may be the strongest. (Nice one Kelly) I use a loop that I learned as The Orvis Knot, over the past 20 years there has been some discord as to who came up with it but the end result is a loop of leader through the eye of the fly. This type connection allows the fly to ride freely and not to be jammed by the knot.
The strength of such knots is derived from the fact that the portion of the material which forms 'the loop' has not been subjected to any strain or friction because it is not the knot, it is independent of the knot and so the material will provide the maximum tensile & torsional strength that it was manufactured and tested for.
This is an animation for the knot I have been using since 1992 or so; Orvis Knot Animation | Fly Fishing Knots
In leader sizes 10 pound down to 7 X I use 3 passes with the tag instead of the 2 which the demo shows. What you get is a slip knot connection with the hook eye in the untied loop.
I will be trying the loop Kelly posted for my streamers until the ice comes.