Here's one a bit different than the others posted so far.
When it's time to fish with itty bitties and I'm out of flies, I usually poke around the flyshop bins for Rene Harrop's latest and greatest creations.
But when it comes time to tie my own I try to keep it simple (the kiss principal).
Small flies are hard to tie no matter what, especially for old farts with fading eyesight.
Hence the Ducktail Mayfly. This one is tied on a #22 scud hook.
This fly has two materials: duck flank and Zelon. The duck flank forms body
and wings simultaneously. The under-mounted Zelon crossbar legs keep it all afloat.
This fly is (relatively) easy to tie. It's durable. Floats well and it catches fish.
For small mayflies it's hard to beat.