An allrounder captain is ideal. You can contribute with the bat and the ball and tactically.
For instance, A.Flower (who actually batted better as captain IMO), Hooper and of course Shaun Pollock are modern day examples.
Sreesanth said, "Next ball he was beaten and I said, 'is this the King Charles Lara? Who is this impostor, moving around nervously? I should have kept my mouth shut for the next ball - mind you, it was a length ball - Lara just pulled it over the church beyond the boundary! He is a true legend."