My biggest written grammar pet peeve! My biggest spoken one is saying someone was "pregnant FOR" her kid and not "pregnant WITH." Omg, it makes it sound like the woman is carrying her own grandchild! So, when someone says it, I just want to strangle them for their stupidity! On a more personal note, I have a family member who says "how" when he should say "while" and another who says "all to once" instead of "all at once." Bloody crazy!!! Lol