On Accident?
Granted, I hear this more often than I have ever seen it online...
Verbally Disadvantaged
"I ran the red light on accident."
Me
"Is it 'by purpose' that you use the phrase, 'on accident'?"
Verbally Disadvantaged
*confused look*
Me
"You should say '...by accident...' and '...on purpose...', not the other way around."