She interrupted me to say it, as I was in the middle of a transaction with another customer, but her tone made it sound like if I didn't drop everything for a quick second she was going to flip out. I could have pointed out that there are bins of paperclips everywhere in the store but her eyes were already accusing me of not taking her as seriously as the line that normal civilized people were patiently waiting in. So I excused myself for a moment, walked over to her, reached into a paperclip bin, and set a paperclip on the counter in front of her. I returned to my customer.
"Okay, smartass. Now go get your manager." Who knows what this cow wants, I really don't care. My manager isn't going to write me up over a paperclip. I made eye contact with my manager and motioned my head in her direction. I continued helping my customer, and listened to her vent a few feet away.
C: "Do you see this?"
M: "Mm-hmm."
C: "This is what your employee handed me when I asked for a paperclip. This is unacceptable."
M: "...Because it's bent? I can give you another one."
C: "He did it on purpose! He acted like I was wasting his time and he bent it to spite me."
M: "I'm sorry you didn't get a straight paperclip but I think you may be over-reacting."
C: "Listen, I'm an account holder! I expect to be treated with more respect than this! I needed a paperclip! I need to keep my documents together. I can't use this and I don't deserve the disrespect of being handed something like this! He just bent it and threw it at me like 'get out of my face' and walked away!"
M: "... ugh. Alright, look at this bin." lifts up paperclip bin "A lot of them are already a little bent. Sometimes they just come that way. Can I get you a new one?"
Customer grabbed one in a huff, put it on her documents, slammed the bent one down by my manager, and stormed out the door, but not before turning and saying that I needed to be dealt with.
My customers that I was helping were completely transfixed by this whole fiasco. My manager walks by and sets the paperclip in front of me as he goes. I picked it up and examined it, "This isn't even noticeably bent", I remarked. M: "Yeah. I know."

P.S. I should point out that saying "I'm an account holder" means nothing, really. Accounts are free and anyone can get one. It just gives you like, a loyalty discount basically that amounts to like ten cents on the dollar.
P.P.S. "I'm an account holder!" is now an inside joke.