I'm often on the lookout for birds passing in front of the sun or moon when conditions are right.
Here, two Canada Geese pass in front of a setting sun which was surrounded by clouds, leaving a sort of hole. This was the best one from a burst of about 6 shots. As I tracked the birds, as soon as I start seeing the sun in the view-finder, I close my eyes to protect then, and hope that the follow-through and auto-focus does the trick. Never look at the sun directly through the lens.
Canon 5D Mark III with the 500L f4 lens with the 1.4 Extender II handheld @ 1/1000, f40, ISO 800, +2 exposure compensation. Slight crop for composition purposes. A multitude of mini sensor dust specks cloned away.
Cheers,
Mike