Post an anime that drew you in from the very beginning.

Hmm, there are a few that've done that, but I'm gonna go with Magi: The Labyrinth of Magic on this one. Everyone was raving about this show, so I went to take a look. 2 minutes in and I was hooked. The settings and opening were what really got me interested in the beginning, but the characters grew on me pretty fast. If you have yet to see this, I highly recommend it. (What is it with me and writing a short novel whenever I answer a question?)

Madoka Magica

Pretty Rhythm Rainbow Live. I watched four episodes of it in one day.

Danganronpa

How does this intro not pique one's interest...

Yuri on Ice. I think I watched the first 6 episodes in one day