Recons are notoriously easy to see once you recognize that they cause diagonal distortions on horizontal and vertical patterns, resulting in a paradoxical sense that an object that is normally flat appears to be much more fuzzy than expected.
Being cloaked does not stop your footsteps, either. I've killed cloaked Recons through sound alone.
Also, HEAT vision allows you to see Cloaked recons, so it's not like you're firing it blind.







