I don't know about the rest of their merchandise but in groceries, if you produce a coupon or an ad showing the item cheaper somewhere else, Wal-Mart will match the price.
I had a lady ahead of me at a checkout counter who had a list of items and prices on notebook paper and the clerk accepted it and gave her the items at the cost listed on the paper. I asked the clerk why they would allow that and she told me it's better to lose a dollar or two on a sale than to lose a customer.
I also like Wal-Mart's return policy. You don't need any excuses or explanations, Wal-Mart will take it back and refund your money. They have such an upper hand over the manufacturers that they can demand them to take an item back or run the risk losing Wal-Mart's business for their product.
A local food store I shop at has the policy of meeting competitor's prices if you show the coupon. I had the unfortunate bad luck to be behind a lady who had a fistful of coupons. The clerk dutifully processed each coupon, and then the lines got longer at all the rest of the stations because our line wasn't moving. The manager didn't get off his sorry butt quick enough to open up another register so soon there were about 30 pissed off customers.
Their policies are pretty good. But I tried to get a bottle of Tabasco Chipotle Sauce at Wal-Mart last night, and they didn't have it. My neighborhood grocery store does.
I like their return policy too. Recently I bought a new microwave from them. It quit working and I just took it back with my receipt and they gave me no hassle. Returned my money. For their fairness I purchased another one from them. A different bland of course.