Practicality and cost consciousness is often a strong enemy of function and style.
And more often than not practicality wins out. One of my favorite functional yet completely unpractical design and performance elements is the side exit exhaust. There is just something about sacrificing convention and standards in order to gain some performance. The unique sound is a bonus also. Seen only on a few models now it's a treat to see this exhaust combination every once in a while.
What's your favorite unpractical yet functional feature?