[m463]

In Borderlands: The Pre-Sequel/Claptastic Voyage there's an enemy called an Adbug.

"While technically hostile, Adbugs do not directly attack Vault Hunters. Instead, they follow their targeted Vault Hunter around and beam a semi-transparent advertisement at them, which is placed in a random position on the field of vision, obscuring part of the field of view."

You can tell when you're being attackd by an Adbug because they beam audio advertisements into your head.