Best prepaid cell phones?

I am looking for the best prepaid cell phones in USA where I am planning to reside for three years. As my company has sent me to California for three months, I am willing to be with only prepaid cell phones. because, I have not to stay in USA so it would be better to pick prepaid cell phone plan. it would be making me save my earnest money also. So guys, please help me to be with the best prepaid cell phones. I am going to point towards any particular phones or providers. Please post your comments as soon as possible.