Barnacle Grapple

The Barnacle Grapple is a detached Barnacle which can be used as both a weapon and a grappling hook. Its tongue can be shot out to latch onto organic objects, such as enemies.

Tactics
The Barnacle Grapple is most useful for latching onto Xen moss, occasionally bearing ammunition for the Spore Launcher weapon, and pulling the player to otherwise inaccessible places. It is also useful as a handy melee tool to devour headcrabs and shockroaches.

The gun has a secondary trigger, to make the Barnacle keep its tongue out to let its user come down more or less to safety with less or no injury.

When latching to a larger creature, the user will be pulled along with the gun instead of the creature pulled towards the user, but may nonetheless be eaten the same way as smaller enemies.

Half-Life: Opposing Force
In Opposing Force, Black Mesa scientists (specifically Walter Bennet) have been able to successfully detach a Barnacle (named "Specimen 1176") from its point of gestation, in good health, but were only able to coax it into latching onto organic matter, such as creatures, fungi and moss, and convert it as a portable weapon, named the Barnacle Grapple in the game menu. Adrian Shepard equips this unique creature as a weapon, after hearing a holographic message from a scientist to Walter. Shepard then carries the gun with him on his quest through Black Mesa until finally reaching the Gene Worm. Here, he uses it to defeat the creature, by bridging a gap to reach the second cannon. When Shepard has killed the Gene Worm, a giant portal envelops him and sends him into a V-22 Osprey, but without his weapons. Whether they were placed in stasis by the G-man, or simply left in the facility to be destroyed is unknown.

Trivia
While holding the Barnacle, it squeaks and moves its fangs for an unknown reason, though it has been speculated that it is in pain.

List of appearances

 * Half-Life: Opposing Force