Just in case you didn't feel bad enough about crushing or burning murderously friendly turrets in Portal, an enterprising engineer has built a real-life version of our favorite stationary weapons. Created for the excellently-named "Advanced Mechatronics" class at Pennsylvania State University, the turret is equipped with an IP webcam and two servo mounts with Nerf guns attached. The camera reads RGB colors and connects to a computer running MATLAB, which lets it identify simple triggers like the bright shirt shown in the video. When it sees the shirt, it locks on and tracks it, so it can shoot if the wearer stops moving or issue a familiar "Will you come over... here?" if they go out of range.
Right now, it's not all that fast, and it has a two-dimensional outline rather than a full body. Its creator says he'll be improving the software and molding a shell soon, so the turret won't look quite so easy to tip over. Although we're sure that if you did accidentally knock it down, it wouldn't hate you.