My most useful photography-related acquisition of all time has nothing to do with the process of taking pictures, per se. Instead, it has everything to do with what I do with the camera in between shots.
For years, I carried my camera around my neck, as many other people do. Now, I use a not-so-lightweight DSLR with rather hefty lenses. My neck hurt enough after a couple of hours to put the camera away to my bag. Of course, as soon as I would perform that maneuver, an interesting perspective would present itself, and I would pull the camera out of the bag away. Wash, rinse, repeat. Hardly ideal.
Then, about a year ago, I came across Joby Sling Strap.
I would never guess that carrying the camera on your hip is so much easier than around your neck. Such a seemingly simple implement makes a huge difference. No more neck or back pain at the end of the day.
Grabbing the camera to bring the viewfinder to the eye level is more of a one-handed exercise than lifting it up from the front, and I actually feel that it is a more natural movement. Furthermore, it is now much easier for me to put the strap and the camera underneath a jacket and protect it from unexpected rain or unwanted attention, while still keeping it at-the-ready.
And then, there is the veritable gunslinger look that differentiates me from any other tourist in the area 😉