I like to trail run - for physical fitness and/or to get to the next shot faster. The 28 f/2.8, with its tiny size and light weight, is a good choice for this activity. On this particular day, I knew that the weather was unsettled - and perhaps setting up for a great shot. I also knew that rain was in the area and likely to hit (note that rain always looks the worst from inside).
I mounted the 28 f/2.8 IS to a 5D Mark III, grabbed a 58mm Circular Polarizer filter, put all in a Lowepro Toploader Pro 65 AW (for rain protection) and took off for a run. Sure enough, about 2 miles into my run (and about 600' of elevation increase) it started to rain. And this beautiful rainbow appeared.
I quickly installed the CP filter and began looking for an interesting shot. The above image, though not amazing, was my favorite from this run. It was shot handheld at a non-remarkable 1/25 sec.
Non-remarkable until you consider the distance/elevation gain I had just run (very heavy breathing), that I was holding the Lowepro case upside down and open over the camera (for rain protection) and that I was shooting one-handed. I love IS.