Im surprised the consensus is not legal writing as that class requires the most work. Of course what you perceive as difficult will be based on the professor, but conceptually torts may be the easiest class in law school (its nice when every rule is a simple list of elements). When bar study comes around everyone looks at torts as the subject to get easy essay points.
And the economic based approach, I am guessing you must go to University of Chicago. I like the 5th circuit law and economics reasoning. Too bad, but I doubt we will ever see one of those judges in the supreme court.