My son had a required CS course at UC Berkeley taught by a professor who didnt want to deal with undergraduates. To discourage them he graded his exams more or less as follows: 5 points for getting an answer completely correct, no errors at all; -5 points for any error in the answer, no matter how trivial; 0 points for not answering. Not answering any question was probably a B, but there was such an uproar from the students that the class was turned into pass/fail. My son opted to take it the following semester from a different prof.
Mathematics at Cambridge is graded in a similar (but far more complicated) interesting way[1]
(This is a simplification) - Questions are graded out of 20 and can also be awarded a quality grade. Answers scoring 15 or more are awarded an alpha, those between 10 - 14 inclusive a beta. Alphas and Betas are extremely heavily weighted - the score for the top students is 30 alpha + 5 beta + raw score, so a single question scoring 15 is potentially worth 45, quality is much more important than quality, the pass/fail line is 2 alpha + 1 beta
My wife had an advanced mathematics course (University of Washington) where leaving an answer blank was worth 30% of the possible points. Any attempted answer was scored starting at 0.
This was meant to discourage hard-to-grade, crappy attempts at scoring a few points. Students would skip problems they didn't think they could answer well and focus their attention on problems where they thought they could put together a fairly solid answer.
