It has been 5 years since I've spent a penny at Walmart, despite the fact that there is one within 3 miles of my house, and the nearest Target is about twice as far away. it was a series of incidents that brought me to my breaking point.
First, I tried to buy fabric. I looked around in vain for an attendant to cut my fabric. Nobody came. I finally hunted someone down in the store, who said he'd page someone to the fabric counter. 10 minutes pass, nothing. So I go up front and ask for help, go back to the counter, wait another 5 minutes. Nobody. Finally, I picked up the phone at the fabric counter, called the front desk, and asked someone to be sent to the fabric counter. Nobody. After about 45 minutes of waiting I just picked up the scissors and cut my fabric myself, brought it to the cashier, and let them to deal with getting pricing. Then they found someone.
Second, at one point I bought a few plates on clearance to use for my friend's shower. I ended up not using them, and didn't want them cluttering up my house. So I went to return them. The woman at customer service range them up, then said, really snarkily "ONE dollar? You're returning these for ONE dollar?? Why are you wasting my time?" I don't know why I didn't demand a manager, but instead explained my reasons. She ended the transaction with a sarcastic, "Don't spend it all in on place."
Third and final, I gave them a manufacturers coupon for a product (for ONE dollar, again!). The cashier rang everything through really quickly, and right as he was about to hit total I asked, "Did you get my coupon?" He had a look on his face that just told me he didn't. Instead of owning up to the mistake, he then LIED to me, and said they only took Krogers or Walgreens coupons.

Uh, no, obviously not. I argued with him, and then he sent me to customer service to wait in line for $1. At least the woman didn't give me snark this time. So I finally called the manager on my way out of the store. They hung up on me.
So I sent an angry email detailing why I was never shopping there again, how I hated them, etc. I admit I was a bit over the top. They had a manager call me, and I apologized for how scathing my email was, said I probably over reacted. His response? "Yeah you did. Next time, just call a manager."
Yeah...there will be no more next times.