Can I change 10.8.2 Mountain Lion window corners from rounded to squared?
I found a thread that describes how to accomplish the question asked.
To fix this I installed this artfile hack:

This is just a simple artfile hack that removes rounded corners on windows, the fullscreen button, and replaces the standard traffic lights with the stiijo ones (that fade almost completely on background windows)
I made it because I found it incredibly annoying to look at rounded corners when using my tiled window manager xnomad.
Download: http://d.asgeirsson.is/obtv (Remember to back up your old (S)ArtFile !! This has only been tested on 10.8.2)