Like Larry, I'm a fan of the pull type razor saws.  The extremely thin kerf is a blessing not only in wood that isn't turned into dust but in faster, easier cuts.  My pruning saws are of similar design with a thicker blade and most are folding.  I don't think these razor saws or pruning saws can be easily sharpened which is a detractor over a saw that can be sharpened with a file.