Robert Pagliarini of CBS has written an article called '5 phrases that will get you fired'. The phrases are "There's nothing I can do,' "It's not fair," "That's impossible", "I wish," and "But we've always done it that way."
I work in a job where people every so often get fired- as one does- and where all five of these phrases have been tossed around with some measure of regularity. Nobody, to my knowledge, has been fired for any of them. They cause mild irritation at worst, and often are perfectly legitimate things to say. The most common phrase that gets people fired at my workplace, from my observation, is "I'm not coming into work today." And even then you have to repeat it over and over in rapid succession.
This is not the first 'phrases that will cost you jobs' article out there, and it won't be the last. But they all dance around the phrases that will ACTUALLY get you fired in a hurry. They all look like 'phrases you're taught not to say in a workplace training video' rather than phrases that you can't say in the actual workplace. If you need to get fired, there are far more efficient things to say. For example:
"Attention customers: my boss is ramming his genitals up the tailpipe of your cars, right now."
"Nice shoes. Let's have sex."
"This is a stickup. Put all the money in the bag." (NOTE: you will need a gun for this one)
"I've peed on everything!"
"I've poured other people's pee on everything!"
"Attention customers: you all are not fit to (insert favorite sex act here)."
"Surprise boxing match!"
"Hitler was misunderstood."
"My anus has been surprisingly clean lately! Here, look!"
"It's fine. That's close enough to age of consent."
"Your cancer is amusing to me."
"You know what my favorite ethnic slur is?" (NOTE: If you have not been fired after asking this question, try answering it.)
"Attention customers: we are now announcing a sale. Everything in the store is free!"
Really, now, Robert. Use your imagination.