A secured card is not an option for businesses. Those are not offered however secured business loans using cash or CDs are easy to get if your security deposit matches the loan amount.
Almost no one will approve credit for a new business without a personal guarantee. You will need credit from trade associates (suppliers) in teh name of your business for at least a couple of years before anyone will give you credit. Beyond that, AMEX, visa, and mastercard are roughly equally easy to get.
This is true. Advanta was the only business credit card issuer that would accept newer businesses without a personal guarantee but that company went under during the financial collapse a couple years ago.
Regarding what are the easiest business credit cards to get approved for, if a personal guarantee is given most will have comparable requirements, with the exception of the American Express Platinum Business Card which is more strict.
Credit Card Forum maintains a sponsored ranking of the best business credit cards that I would recommend checking out. It also discusses the personal guarantee issue.Compare the best business credit cards