I think the reason the inverse square root function got so much coverage was because of the bithacking of the float format, and the apparent WTFyness of the code. Also didn't it use Newtons method, not a Taylor series expansion? My math at that level is stale.
It did use Newton's method, and the cool part was that with a carefully-chosen initial value, you only had to run 1 iteration to get a reasonably good result.
