Apple Pay

That gets into interesting histories. There was a merchant consortium that intended to create their own payment system. Many of those merchants abandoned the initiative in favor of accepting contactless payments, Walmart didn't. So, they are a big hold out.

Here is some general information: https://support.apple.com/en-us/HT208087

Otherwise, Walgreens, BP, Starbucks, Chipotle, etc. all accept Apple Pay.

As do a lot of local places, Wynkoop, Great Divide, Aviano coffee, many fast casual restaurants and most small businesses that use Square.

Pretty much anywhere that you can use contactless payments, you can use Apple Pay. If you're looking for specific information about an individual place, do a quick search in maps and review the details of the store or venue.