From electronics sales...
When you ask for "top of the line", don't do any of the following:
1. Whine about how expensive it is. "Top of the line" Q-tips are relatively cheap. "Top of the line" electronics are not.
2. Seem upset that the first thing I showed you was the most expensive piece- "top of the line" is usually going to be the most expensive.
I can understand that you installed a large home theater system with speakers and such, and you overestimated how many spools of wire you needed... NO, you cannot return a spool of wire that was partially used and is now incomplete. Telling me you used "about a quarter of it" and asking for a refund of 3/4 of the price you paid, will make me laugh at you.
When the employee standing next to me is also laughing, and you ask for the manager, don't be surprised that he's the other one laughing at your dumb ass.
From cellphone sales...
No, dropping your cellphone in the toilet is not covered by your manufacturer's warranty. If you don't have insurance, I can't just GIVE you another one. No business on the planet operates that way. If I drop a toaster from Target into a lake, I cannot go back and get a new one for no reason- I don't understand why you think this would work with a $300 cellphone. (and you may laugh, but you wouldn't believe how often people drop their cellphones in their toilet)