The following phrases really annoy me:
"...have your cake and eat it, too." What exactly is the point of having cake if you can't eat it??? People always use this phrase to mean that people are expecting too much and being unrealistic, as in "You just want to have your cake and eat it too," but I challenge you to find one person who wants to have cake but not actually eat it. Who wants cake just for decorative purposes?
"It's always the last place you look." Well, yes, obviously. Because once you've found whatever it is you're looking for, you stop looking. So, the place you found it is the last place that you need to look.
"My bad." (When used in place of "I'm sorry.") For example, someone will accidentally spill something on you and then say, "My bad!" Um, are you claiming responsibility? Because I kind of already knew it was you - an apology would really be more appropriate.
"Quote... unquote." You can't "unquote" someone. It's supposed to be "Quote... end quote," as in "This is the end of the quote I was sharing." (My fifth grade teacher explained this to us, and it's annoyed me ever since.)
I'm sure I'll think of more phrases I hate later. In the meantime, what phrases do you hate?