Every once in a while a fly pattern comes along that's so buggy it can successfully imitate lots of different kinds of trout food with ease, grace, and effectiveness. Dave Sloan's Paralyzer is a perfect example of just such an "impressionistic" fly design.
What makes this is an exceptional pattern is the Parachute hackle and the caddis-type wing that resides on the top of the shank. As a result, the fly rests well within the surface film presenting a clear view to the trout. The wingpost makes the pattern quite easy to see and the heavy hackling gives this fly great floatability in turbulent waters. Either Hollow Deer Hair or Elk Hair can be used for the wing. The preferred presentation of this pattern is an upstream cast allowing a drag-free drift through runs and riffles.