There are some aircraft that have been built and flown in huge numbers which it is almost embarrassing to admit that you have never photographed. One such aircraft is the Antonov AN-12. This was a ubiquitous military transport for the eastern bloc and, while it is now a rather aged design, it still has a good role as a civil freighter. However, I have never seen one in action until recently.
A Ukrainian registered example from CAVOK Airlines was coming in to Seattle. It was due to arrive at around 1pm which meant the light would be right on the nose. The worst possible case. Of course, that was assuming that there would be light. When it actually arrived, the sun was well obscured by clouds. Given the dark colors of the plane, maybe that was a good thing. Two minutes after it had gone, the sun was back out of course. It was trailing smoke from its old generation engines but it was definitely a highlight of the last few months of movements.