Ken Arrow is awesome. The Impossibility Theorem is what convinced me to go into an econ PhD program. He's definitely on my list, but probably not at the top.

It might be a boring answer, but my favorite economist is Mises. The socialist calculation problem was such a brilliant insight and Human Action is the most extraordinary econ treatise.

Of living economists, Bob Murphy is my favorite. He covers such a wide range of topics that I'm interested in.

Amongst living mainstream economists, I'm a big fan of Emily Oster's work on family economics.