Barnacle

From the Half Life Games comes this creature known simply as a barnacle it hangs up on ceilings waiting for prey to wander right under it then using it's long, strong and sticky tongue it grabs them, usually by the throat and drags them up into it's gaping mouth that can expand a little to swallow easily a whole human it's digestion can easily handle human and even some wearing armour or special suits.

However it's rather strange, even if shot it only stuns the creature for a minute, so how to kill it is unknown right now.

Barnacles can be usually found in abandoned Research Facilities, maybe Dark and forboding caves and other dark places to help with it's ambushing, it also prefers tight corriders making it hard for prey to avoid it's tongue.