The Stimulator is one of the best known attractor patterns there is. The fly is tied in a great number of variants and colors. It can be fished as a stonefly or a caddis pattern,as well as a general searching fly. I use it mainly when the weather is rough or the river runs high. Tie it in any color to suit your needs.
The grey/white variant pictured below is my choice in the autumn,when big moths constantly crashes into the water in the evening. It works exceptionally well in my local river at that time of the year. It is supposed to be scruffy and roughly tied.