I enjoy working with any size data set. I work with large data sets in my current day job(millions of rows of data). I use excel (v and h lookups, pivots, slicers, graphs and charts) as well as Microsoft access to manipulate data sets over one million rows. For these larger sets, it helps to compact the data so that excel can handle a summarized version of the data and summarize it.
Right now, I am studying for the US CPA exam and I like to keep my skills updated manipulating data.