Death Note

Any notebook that kills the person who's name is written in it.1)2)3) These notebooks are usually carried by shinigami, but on some occasions, people are found in possession of one.

1)
They will suffer a heart attack and die 6 minutes after their name is written
2)
If the cause of death is not written within 40 seconds of writing the person's name
3)
This means one could do almost anything to manipulate a person before killing them