It is an ability that a scant few first-person-action games grant you, and one that becomes an obvious and natural part when included, and its absence painfully felt when forced to play without it.
Kicking should go hand in foot with shooting.
For me it started when I first played the greatest FPS game ever made; First Encounter Assault Recon. Since then any FPS that has included Kicking has immediately placed itself in a special league above all other FPS games to me, regardless of other factors or aspects.