The on campus interview was a fairly straightforward interview, except for when the interviewer pulled out a page of data, explained the background for it, and asked me to walk him through how I'd determine which of 5 items to pull from the shelf and which to put more support behind.
None of the individual on site interview questions were particularly difficult, but they covered a broad range of question types.
The first was a fairly standard interview with some behavioral questions (strengths and weaknesses, tell me about a time when you ___, tell me more about this item on your resume, why are you interested in this job, why do you think you'd be a good fit, etc.).
The second was primarily designed to assess how I think/analyze things (give an example of a good and bad ad campaign, what questionable assumptions does this ad make, how would you figure out how many dollar bills would fit in the Empire State building, if you have 2 baskets of black and red balls, how would you arrange those balls to have the greatest chance of someone picking a red ball at random, etc.)
The third seemed to be designed to assess which area of the company would be the best fit, whether my skills and interests are a good match for the company, and if it's in line with what I'm looking for in a job.