My little brother and I both love Portal (and of course Portal 2). We decided to both draw a picture of GLaDOS using his colored pencils. This is what I ended up with. I didn't spend too long on this; I worked within the attention span of a 7 year old. And I know some of the feature of GLaDOS are probably waaaay off, but oh well.
Update: Thanks to everyone whose added my sketch to their favorites!