Think about when you first played the game, you're roaming through the wastelands, you've already killed a few raiders and picked up some half decent weaponry and are starting to feel like Mad Max. You head into a new area, DC or somewhere and you see a new kind of enemy, he, she or it is coming at you, and you hit the V.A.T.S. button to get a closer look, and you think to yourself 'WTF is that??!!' before engaging it.
For me, the Centaur!! Completley grossed me out.