It doesn't really have to be your best photograph—just one you like!
Please be sure if your photo contains people other than yourself, that you have the explicit consent of the people in the photos before posting them.
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Here's one I took recently of a squirrel taking a morning nap, its fluffy tail curled up over its back. It's not a very good photograph technically, but it's the best I could do without waking the squirrel. As soon as I crept closer, it woke up and scurried down the tree trunk, where a younger member of its clan immediately pounced and began a rip-roaring game of CHAAAAAAASE!