Talk about ugly bitches. And bad hair days (HAW HAW!). Is she the coolest female monster of all time? It's debatable (you'll see I've ranked another one higher), but she's one of the few female monsters ever, and unless someone else can prove me wrong, she's the first female monster ever created, period.
My favorite depiction of MEDUSA is from the wonderful CLASH OF THE TITANS film. The Ray Harryhausen design of Medusa is amazing. The scene where Perseus is trying to kill her in the temple scared the shit out of me when I was a kid watching it in the theater.
Did I mention she had big ass snakes for hair? Jesus Christ, that's some scary shit.
What was really cool about MEDUSA is that not only would she turn people to stone that looked at her, but even after death, she was pretty dangerous. Her blood would cause giant scorpions to sprout out of nowhere, and her severed head was still powerful enough to turn the Godzilla sized KRAKEN to stone, too.
The stop motion effects in CLASH OF THE TITANS were Ray Harryhausen's last hurrah. Sadly, this art form has gone the way of the stop motion dinosaur, as computer animation is more realistic and, more importantly, cheaper, but the TITANS depiction of MEDUSA is one of the best examples of that art form that movies have ever showcased.