Shenron  

Although this Dragon can only grant one wish, he is used the most in Dragonball and Dragonball Z. After a wish has been made, the Dragonballs are scattered to the corners of the earth. Once someone collects them and a year has passed, you can once again make a wish with the dragon. The dragon was created by Kami, but, when Dende became guardian he re-made Shenron to be able to have more wishes, and for those wishes to be more powerful than before. You cannot wish for someone to be killed.