It's always the short (<30 episodes) anime series that get me, and Elfen Lied is NO exception. At a mere 14 (13 + 1 extra OVA) episodes, I was kind of doubtful it was gonna be any good when my friend recommended it to me.
I was wrong. Best, most intense, most depressingly emotional show I have ever watched.
This thing is a masterpiece. Instantly became my favourite anime (and show) of all time, beating out Death Note and the like.
HIGHLY RECOMMENDED! In fact, I pity those who have not watched this. Some people are turned off instantly by the gore and nudity, but these people are ignorant pussies (to put it bluntly).
PS: Don't forget to read the manga to find out the REAL ending. Yes, the manga IS better than the anime, and that's saying something.