The first time I played Fallout 3 and had never played the previous games, I was adventuring and came upon Old Olney so I could get to a Vault (92 I think) and went inside, got bored quickly, left, who was charging at me?
A Deathclaw.
Now I knew nothing of Deathclaws before that and as such nearly shit my pants when I saw the little red Icon then looked in V.A.T.S casually to see if I was getting a Bloatfly, Rat, or maybe even a Dog, but instead saw what reminded me of a brownish Satan.
I proceeded to save my game like a tard and get murdered.
Second time I knew he was there and used a Stealth Boy, but for some reason he saw through it and proceeded to kill me again.
It went on and on like this, fighting, dying, laughing, panicking, until finally, I SLAYED THE BEAST.
I never ran into another Deathclaw, but from that point on, whenever threatened by a Super Mutant or Raider, I'd kill em, run up to their bodies, grab their heads, and fiddle with it while yelling "I KILLED SATAN! YOU'RE NOTHING TO MEEE!"