What are your favorite examples of evolution in progress?

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Sometimes you can see evolution in progress, and I find that really cool! My favorite example is the halibut:



It's evolving from having eyes on either side of its head and swimming like a normal fish to having its eyes on the top of its head and swimming flatly along the ocean floor. Clearly swimming flatly and hiding in the sand is beneficial for halibut. However, it's not there yet, so it's a super ugly fish for the time being.  

Does anyone else know of any other interesting partially-evolved features of species like this?

Partially evolved? O.o;

There is no such thing.

I know what you mean (because everything is always evolving) but I'm talking about a specific feature of a species that is not yet optimized for the purpose it serves in a specific niche, and is undergoing a distinct change. Like the halibut's eyes. I don't think it's wonky face is the best adaptation for visibility while swimming along the ocean floor yet.