Recently, DH has been getting really annoyed when people say "24/7". He thinks the correct expression is "24 hours a day". This doesn't bother me, but I really hate when people say "I could care less" when they really mean that they couldn't care less. Some other things I wish people could be persuaded not to say :
"Irregardless" -- This is not a word! It's "regardless" or "irrespective" not a combination of the two.
An old roommate used to apply "more than life itself" to just about everything, for example "I hate that class more than life itself" "It's more annoying than life itself" If I hadn't understood that she didn't have a clue what she was talking about, I'd have thought she was a suicide risk!
There are more, but I can't think of them at the moment. What are some things that you wish people wouldn't say?