Death Note
Death Note is a manga by Tsugumi Oba and Takashi Obata. It follows the life of Light Yagami after he finds a mysterious notebook with the words "Death Note" written on it.
The Death Note is a tool for the shinnigamis, specifically Ryuuk who owns the Death Note that Light finds. When a person or shinnigami writes a person's name in the Death Note, that person will die. Either by a heart attack in (I think) a half hour if the cause of death is not specified or by any means that the writer puts down in the Death Note. There are a bunch of rules to the Death Note but I won't go over them here.
Light himself is a good kid. He's a straight A student and has a good heart.
Or does he?
*Spoiler Free*
The manga and anime are both very very good. The best parts are the drama and character development as the story progresses. It keeps you watching/reading it from beginning to end with no lags.
Pretty Pictures

Light(in front) with Ryuuk

Misa Amane - quite possibly the most annoying creature in anime/manga

L - you will love L, or I will hurt you.
~Fin