One of my favorite devices in photography is depth of field. I spend ridiculous amounts of time thinking about it, playing with it, planning it, trying to alter it, and mostly failing at using it to my advantage. I could possibly go to the trouble of buying a new lens, but I'm on this whole, "live within my means" kick and what I want is expensive... and it needs a new camera attached on the other end.

Of course, if it got me a job working on the next 3D blockbuster movie, it might be a reasonable expenditure.