Well, aside from South Park? Hmm...
Someone already mentioned Faust, and Jan Svankmajer's film version features a -very- interesting portrayal of Satan.
http://www.imdb.com/title/tt0109781/
A flash artist by the name of Matzerath has created many hilarious portrayals of Satan.
http://matzerath.newgrounds.com/
Chris Valagao of the metal band Zimmer's Hole built his image around the devil, and as seen in this music video, it's a very over-the-top persona.
http://www.youtube.com/watch?v=QpAA-NBUqYk
Deathrocker also mentioned Deicide in the realm of music, but it's the satanic black metal bands of Norway who do it for me. There are many stories of various bands with members going to prison for murder and church arson in the early 90's. Out of all the bands, Gorgoroth is by far the most compelling with their satanic imagery. In Poland, they're infamous for putting on a show with satanic imagery that was so shocking, they were banned from the country. All footage of the show was confiscated, but there are a few images from it on the internet. But I can't really recommend Gorgoroth or the Norwegian black metal scene to anyone without an existing interest in metal.
And on the opposite side of the coin, by far the most fascinating portrayal of God is in Begotten, which is easily the most disturbing film I've ever seen. No Satan in this title, though...
http://www.imdb.com/title/tt0101420/