Rice also has a very successful Honor Code, though I'm not sure how it differs from that of Caltech. At Rice, it means that many (most?) exams are not even in-class. Students are trusted not to cheat and are allowed to take exams home. If the professor says that it is a one hour closed-book exam, you are expected to adhere to that. Of course, there are in-class exams as well; it's all up to the discretion of the professor, but my experience was that many teachers embraced the Honor Code.
Violations are punished very harshly. Most violations are reported by other students. And students serve on the Honor Council for deciding how violations of the Honor Code should be handled (and if a violation had in fact occurred).
I'm glad there's another example of this. At Caltech, it was institute policy that exams were not proctored. If they were in class (a rarity) the professor was required to leave the room for the duration.
Another unusual Caltechism is that all classes could be placed out of by taking an exam - and if you passed the exam, you even got credit for it.
Professors were not allowed to take attendance nor have attendance be any part of the grade (except for PE). This had the nice effect of the only people in the lecture hall were people who wanted to be there. Cut ups and disruptive students simply didn't attend.
How did they handle stuff like foreign language courses where there was a speech component? (I remember doing one-one conversations for assessment, don't see how you could escape that).
Violations are punished very harshly. Most violations are reported by other students. And students serve on the Honor Council for deciding how violations of the Honor Code should be handled (and if a violation had in fact occurred).