I'm principally against using a credit card, so I've done a lot of research finding the best debit savings.

Although card companies make it hard for shops to offer cash or debit discounts, they exist. Aldi only takes debit cards and is way cheaper than any other grocery. A Thai restaurant I used to go to always brought us the bill offering 5% off if paid in cash(lots of neighborhood places like this). Any bar will throw on tax if you start a tab, but paying the cash price per drink is usually the exact advertised price.

Paypal debit card offers 1% cash back. Schwab debit card offers rental car insurance and free foreign transaction.