Navy Federal Credit Union http://www.navyfcu.org as low as 3.9%
But USAA has a program out for newly commissioned officers, forget the exact details, I purchased a honda after commissioning, was a really low interest rate, the catch is that you have to have your check direct deposited with them for the term of the loan. Honestly, USAA between banking and Insurance is one of the best banks you can run across. IMHO