Gargantua

Gargantua, as seen in Half-Life.

It's equipped with two, claw-like, hands which, when it's pursuing a hostile threat, can open up and emit intense heat, much like a flamethrower. Even though the range of the fire is quite puny, it deals a great amount of damage if the threat is caught in the middle of it. As for medium to long range targets, the Gargantua isn't vulnerable there either. It can also emit a powerful shockwave towards its opponents by giving a powerful stomp onto the ground. Although the shockwave is slow moving and can easily be dodged, it travels on any surface, flat or blocky, until it reaches its target.

While the Gargantua is a vast powerful creature, can withstand any conventional weaponry, it's vulnerable to explosives and high-energy weaponry.

The Gargantua are both encountered in Black Mesa and on Xen.