Bass Gnomes has released Common Image, a free (and simple) spatial enhancer VST effect plugin for Windows.

Common Image is an effect designed for stereo content. Common Image inverts the left audio channel, and mixes this inversion with the right audio channel, and vice versa. The result is the unique stereo image per channel, and the phasing out of the mono material.

Common Image can shift mono content in relativity to Stereo Content by using the “relative” position, or it can allow positioning of stereo content while maintaining mono content position by using the “grouped” position. 

Common Image is available at no cost on Bass Gnomes.

More info: Common Image VST