Complete and Utter Randomness
There's a guy in one of the Neuro labs over in the Molecular & Cellular Bio Building who doesn't bother with stereotaxic surgery when he needs to inject something into a mouse's brain. He just picks them up, sticks the needle in, and takes care of it. He's apparently done it enough times that he's consistently accurate. I've never seem him do it myself, but that just sounds incredibly awesome.