I think which subject is boring depends more on the professor than the subject. But economy and accounting seem like harder subjects to make exciting. I think economy has been the worst, but that's probably because of the very nice but boring professors. Also the frustration with one.
The frustrating one, was heavily into the stock market, and admitted he was just doing the part time teaching bit for the benefits and retirement package. But anytime you used a hypothetical question using a company as an example (because he'd ask what market or company you're thinking about), he'd answer by saying he can't directly answer that because he doesn't want to mistakenly mislead us to a real world opinion, which may or may not be correct, and lead us to taking a real life action of investing into a stock that we shouldn't, and then suing him and/or the school for wrongly mistaking him. Then we'd have to go back and think about how do we ask the hypothetical questions about a company or market, without getting into the company or market, and it was just a big pain in the butt to get any straight answers out of him, which made the class extremely frustrating.