If I could only have one, I'd probably pick the one that started all of this, the one I worked hardest to earn and the one that has sentimental value.
I'd choose the first Heuer I owned:
The 230.006 Heuer Pilot's Quartz (!) Chronograph... Note all of you quartz owners, I own quartz too!
Back in 1984, the family business was booming to such an extent that I was put in charge of a job site some 65-70 miles away from home, the job we were on needed to be completed with great urgency, which meant months and months of 10-13 hour days, 6 day work weeks and 90 minute to two hour commutes each way every day save Sunday (and then doing the Payroll on Sunday!). We started in late April and went through late October and into November until we completed the job just as the weather turned bad. After getting all the the equipment packed up, transported and stowed for the winter, we were all able to relax a little bit and I was able to to back to our other job site which was under a much more relaxed schedule. It was quite an experience.
Anyway, a couple of weeks later, my father mentioned that he wanted to do something for a bonus for the efforts and sacrifices I had made that year, and I had seen this Heuer in the window and I couldn't think of anything else I wanted more. In retrospect I realize that I probably could have asked for anything within reason, but it's a probably a good thing that I asked for the watch, as It's been a boon companion and lasted longer on other things I could have named in it's stead.
I feel Pilot's model watches are typically the most versatile watches one can own. The presence of a "Whiz Wheel" or Circular Slide Rule, is useful and very handy. Of course Multiplication and Division can be done on a watch so equipped, as can problems involving proportion (for example, if you wish to reduce a 8 1/2" x 11" page to 5 1/2" x 8" page what is the reduction?
A Whiz Wheel watch can also do time x distance = rate problems as well:
In this example, 450 miles was covered in 6:00 Hours, so we line up 45 on the outer dial and 6:00 on the inner, at the big MPH marker at 12 we read the rate: 75 Miles Per Hour was our average.
The Whiz Wheel can also emulate a Tachy bezel. In fact the Heuer models have nifty little red triangles at 36... The significance? 60 minutes x 60 seconds = 3600 seconds in an hour. So in this next example:
We divide 3600 (36) by our time for a flying mile: 45 seconds getting a average mile's per hour of 80 MPH as indicated about 10 on the right hand side of the dial.
The Whiz Wheel is also handy when traveling in converting currency. The English pound is currently (and was also nearly this exact same rate) selling for 1.62 dollars. So I put 1.62 (outer) over 10 (Inner) and I can convert from one currency to another at a glance... Is £12.95 a bit pricey for CD's? Well it's nearly $21.
Another example:
The last time I was in Germany the exchange rate was US $0.67 to one Deutsche Mark... I saw a watch there with a sticker price of 595dm, would I have to pay any customs? Well... with the outer ring at 67 over the inner's 10, I can see that 595dm was about $408, so I would have to pay some, like 80¢.
You'll also note that there are Stat, Naut and KM indications on the bezel, and you can convert between knots, Miles, and Klicks. If you remember any of the conversion factors for English to Metric, you can covert them easily without paper etc. It's also handy for doing Dollar to Euro conversions for eBay bidding etc. The Whiz Wheel can also be used to emulate a Telemetre and Pulsometre as well, but I won't bore you all with the details in this already too long post.
In short the pilot's models are very versatile watches.
While I own a pair of these in the automatic trim (one each in Black and Silver dial trim), if I could only keep one, it'd be the first one which is a quartz.
-- Chuck