VERY good question.
If I had a point system for coolness, this is probably how it is right now...
Sleek aerodynamic design that "looks" fast +10
Retractable gear +10
Taildragger +20
Low wing +5
High wing without struts +3
Three blade CS Prop +5
Canopy +10
Tundra tires +15
Radial engine +35 (in my dreams)
V12 water cooled turbocharged piston engine +50
(but let's be real not gonna happen)
Two engines +20
Pusher configuration +20
So on my scale a 150 with tricycle gear scores 0...
Cessna 182 scores 5 if it has a three blade CS prop
But a strutless Cessna 177 scores 13 or even 15. I think they're great.
Dell30rb's swift scores 45
Everyone is different but that is the beginning of my "coolness" formula after just a few minutes thinking about it. I could refine it further.