Ditto the hornet's nest on one of Hick's caches this past summer. I carried a can of wasp spray and a baseball bat, but the nest had been knocked down. I didn't know that going in.
I found this Mama Robin on her nest in Iowa at GC1PRA5 on 4/28/09. When I first saw her, she was facing me, and so still that I thought she was a taxidermied bird geocache. I stared a long while, wondering if she were real. Finally, she blinked an eye. I ran to grab my camera, but by the time I returned, she had turned around in the nest.