Major English Texts II cheating scandal
The 2013 Major English Texts II cheating scandal involved a lot—a lot—of people cheating in a "notoriously easy" English class at Barnard College. Basically, two things were happening: (1) people were using Google to cheat on weekly reading quizzes and (2) students were paying other students to go easy on those quizzes, which were student-graded. And it turned out that, despite occurring in a Barnard College class most of the cheaters were Columbia College students.
It goes without saying that students shouldn't grade each others' quizzes, honor code or no.
As a result of the cheating, Professor Ellsberg threw out all the quiz grades and added a final worth 70% of a student's grade.