I FIGURED IT OUT!! This looks to be a bug in Unity - without an input device (microphone) Unity crashes. I was attempting to change audio settings on my Mac Mini to see what I could do (turns out there is not much to change on a Mac - big surprise) and I noticed I had no input devices listed. On a whim, I plugged in an old set of headphones into the audio input jack on the back of the Mini. OS X detected the headphones and an input device was listed and... KSP started! This fixed Besiege, City Skylines and KSP!! How do I submit this problem to Unity??
