One of the essential streamers for any flyfisher, warmwater or coldwater, is the leech.  Its large size makes it an appetizing snack for many fish.  The tail of this pattern is made courtesy of the indispensable microfiber mop.  Black zonker strips are wrapped to create the bulky body, and a pinch of black dubbing and a red conehead finish off the fly.
 
Hook size:  Streamer size 6.