Harbor Freight has always been fine with one exception. My mom bought some sander thing there, last one on the shelf, and they kept insisting she get the warranty. She declined and got it home and it didn't work. Months later when I found out about this debacle, I opened it up and it was full of sheetrock rust. Someone had burned it out on the job, wiped it off, and returned it.
Anyway, we did the ol'shifty return as warranty trick. Bought another one, stuck the burned out one in the box, and did an exchange.
Just use some common sense and take a look at it before you buy it. I don't walk into Lowe's or Home Depot without a knife to open up the boxes of anything I'm about to buy either and those employees can give me dirty looks all they want.
That's actually good advice. Here's an interesting note though. Home Depot actually has a policy where you're not
allowed to open a box on the shelves. This applies to both customers and employees alike. I think the intent is to prevent people from stealing the parts. Quite honestly, I never cared for or followed this particular policy. I have no qualms about opening boxes for the reason described above. Though since I've left HD, I do believe they changed their policy to not opening boxes without an employee present. Problem is, there's rarely an employee present.
In a kind of jumbled thought process, I used to work at returns and I was pretty damn good at filtering this kind of returns. I used to fire that ---steaming pile of meadow muffin--- right up in front of the customer and if it didn't work... well... you get the idea. Non-working units were required to be tagged as RTV units, never to be sold by the store. On the sly, I used to take a pen and mark a hidden spot. Over time, I found these marked units on the shelves that were supposed to go back as RTV or disposed of. Come to find out they had hired a "repair tech" (a college kid in his early 20's) to repair those tools and put them back on the shelf. They coined it as "recovery", I'm not sure if it's on the books but selling a used and/or repaired item as new probably isn't exactly kosher.
In the same vein, I've heard rumors that Fry's sometimes gets a hold of the security seals and puts them on returns to avoid green tagging. I've also heard that sometimes that some stores don't green tag. I haven't quite seen this yet, so it's buyer beware.