I really like this, the M2 is already mean looking, this is subtle enough but kicks it up a notch...
http://www.baanvelgen.com/blog/first-look-at-vorsteiners-bmw-f87-m2-carbon-front-spoiler
http://www.baanvelgen.com/blog/first-look-at-vorsteiners-bmw-f87-m2-carbon-front-spoiler