Some time after buying my MR2, I made a driving trip to Niagara Falls and while there found a Niagara souvenir baseball style cap in colors that matched my car. I wore it during that trip and on the way home where I promptly lost it to the wind while driving with the top down. That problem has since been solved by my son who introduced me to cap keepers.
In the mid to late 2000's I got caught up in the Texas Holdem poker craze, and played enough online poker to earn myself a PokerStars cap. For a while this became my official driving hat. A hat with a bill or brim is particularly desirable in a convertible on sunny days.
Having become accustomed to wearing a cap, I started buying them as functional souvenirs of my travels. My first travel cap after the misfortunate Niagara cap was from Cabo San Lucas, and sadly I lost that one as well, tho not to the wind. I must have dropped it or left it somewhere because it just disappeared one day. However, I now have more than a dozen caps that I rotate wearing about once a week. Each one brings back memories of the location I purchased it from and some, like my Maui hat are extra special. A gallery of my collection of 'vacation hats' can be seen here.