[MrWookie]

I'm going to nominate a somewhat unusual one. My pick are the three pecking tentacles in Half-Life that you have to kill by firing up the rocket engine. What's great about them is that essentially the whole level/stage is designed around beating them, and that you have to spend so much time dodging them that they're truly maddening. Most FPS bosses are a glorification of "empty clip after clip into them while dodging their fire" or "figure out the one trick weakness, and then empty clip after clip into that while dodging their fire." The tentacles were a cool change of pace in that you couldn't just kill them, nor were they just spying you and then opening fire. I'm not sure how much the "sound sensitive" mechanic had been used before this game, but the execution here was slick, fresh, and effective. The loud, echoing clangs of their pecking still resonate in every Half-Life fans ears. Finally pushing that button and firing the rocket is one of the most satisfying feelings in any FPS ever made.