I've often experimented with assessment in my classes. I once--somewhat masochistically--asked students to come up with questions for me to take as a midterm. (The point of it was to turn the idea of a midterm on its head, not to find out what students know, but what they don't know, and why. It's a very effective way of finding out gaps in their knowledge and be able to fill it quickly. It was a small class, fortunately, and I changed the format the next time round, asking the students to make their own midterms for each other.)
For all the talk about games-based learning and gamification of the classroom (not sure about the latter yet, will blog about it in due time), I'm surprised the question of assessment hasn't come up as often as it should have. If it does come up, it's usually in the form of using games as assessment (e.g., designing a game that demonstrates your understanding of something). Having worked with some assessment gurus in the past, I'm always pushing myself to rethink assessment and to avoid traditional forms of assessments like the plague, so a few ideas inspired by games have seeped into my head over the years.