I know, that's hard to find. Generally you get one or the other. So I started brainstorming and came up with a few of my favorite leading men who have that quiet confidence.
Westley from The Princess Bride. This farm boy is the classic unassuming hero.
Noah from The Notebook. Swoon-worthy Noah is confident enough to approach Allie but mild enough to let her go.
Atticus Finch from To Kill A Mockingbird. A wise mild man with the guts to stand up for what he believes.
And to completely contradict myself, I do have to admit that there is a side of me that loves the "gods-gift-to-women man". Who doesn't have a weakness for Han Solo, Rhett Butler, and Mr. Darcy? To summarize, even if the book might not be your favorite, a strong leading man will get you through it.