I "could care less." No, actually you mean "you couldn't care less." If you could care less it implies that you do care somewhat..
"This is just so flustrating." No, it is frustrating. I think people have put the word flustered and frustrated together to make this one. (My Mom says this one, but you don't correct your mother.)
The traffic was backed up because someone wrecked their car in the medium. No, they wrecked in the median.(My Mom calls this one "media".)
Well we had went to the store. No, you had gone to the store.(Hey, I'm from Alabama I could go on and on.)
It is very unique. No it is unique. Unique means one of a kind, it cannot be very one of a kind. It either is or isn't, there are not varying degrees of uniqueness.
All for now..Bob