"Hindsight is 20/20" - I cringe whenever someone says that. So overused.
(When there's a missing pricetag) "Hey, must be free!" No, it's not. It's not free.
"Knah-mean?" I have no idea what you mean, I can barely understand what you say.
"Can't take it with you" - Dude, obviously. That's no excuse for stupidity or not planning ahead.
"What doesn't kill you makes you stronger." Maybe. Or it might just leave you in a weakened state. Again, not an excuse for stupidity.
"Cigars are meant to be smoked" (or any variant.) - Do whatever you want with your property, and don't let anyone guilt you into doing what they want because they have sour grapes about not having whatever you have.
(When I was a bank teller, and asked if there was anything else I could help them with) "Got any free money?" - Hey, haven't heard that one before! You're amazingly clever, Mr. Customer.
"Brah" - It's "bro." Not "brah." Don't say "brah."
"Banks are evil." No, sir, you're just bad with money. I didn't cause your seven overdrafts, you did.
"Should of/could of" - It's have. As in "I should have..." Oddly I don't care about "shoulda" at all, that's fine, but when written "should of", it drives me nuts.
"For all intensive purposes" - This one drives me absolutely bananas. The purpose is not intensive. It's "For all intents and purposes." Very different things.