I have a TI
-89 but I've never tried to do anything worse than writing notes to the girl behind me and swapping calculators every once in a while! Not during a test, obviously, during regular class. Note to self, doing this in Cal III isn't smart, because both of us really needed to be paying attention (Cal III is a freaking bastard of a class).
The most prevalent type of cheating is probably simply glancing at others' papers.
Pretty much all of my professors have said that if he catches you cheating, you get a zero. They don't tolerate it. Personally, I've never noticed anyone cheating, but I'm sure it goes on.