The biggest surprise for developers is when your client come and said - I have everything! I will give you mock-ups, wire-frames, clear specification and even will not change my ideas during the iterations. Just make an app! No kind of other news can make much surprise.

I got such one a year and half ago. But it is really some kind of exclusive situation. For all other guys we have decided to make a some kind of test in our website early this year: http://mobidev.biz/project-readiness.html. Hope that in the 2013 I'll be really surprised with some perfect client and will start discussing only the technical news