Median filter: IBA::median_filter and oiiotool --median.

Median filters can be good for removing high-frequency outlier value noise, but without also blurring edges like a blurring filter would do.

Also, IBA::unsharp_mask and oiiotool --unsharp, if you say "median" for the kernel name, will use a median filter rather than the gaussian blur for the smoothing step of the unsharp mask. This tends to have the effect of sharpening small details, while not over-sharpening long edges as the traditional unsharp mask sometimes does.