I have read a number of posts about the usefulness of the chronograph complication and who uses it for what. While I find timing the grill time of a nice cut of steak to be a productive use, I grant you that one could just as well accomplish the same with a much less expensive alternative.
So... I guess I have always wondered if I would use my chrono for something really important.
Lo and behold, I have found such a use!
I am leaving my career of many years to return to grad school - in this case law school. I am taking my LSAT in September, a very important test. In preparing to take the test, which is 6 sections of exactly 35 minutes each, I am told it is very important to pace yourself and practice timing how long you have for each section. The LSAT also has some very strict rules for what can be brought in to the testing site. One of them is that you can have no electronics (cell phone, PDA, etc) which makes sense but one rule that I just learned is that no digital watches are allowed. I assume because some can also store information, though the LSAT is not the type of test you could have a 'cheat sheet' for even if you desired to do so. Nonetheless, only an analouge watch is allowed and I have found that my mechanical chrono will come in extremely handy so that I can have my own time referance to refer to during testing without needing a stopwatch or a digital watch with a countdown feature.
Soon we will have this conversation - "Honey, you know I really need that (AP ROO, Lange Datograph, fill in your own fav) for law school. It is a requirement, you know....." 
D