There are many devices available now days. With that in mind, there are many favicon sizes needed. Here is a great explanation of the many different sizes of favicons, how to design them, and implement them on your website.
If you are talking about it being crisp on certain devices and not on others, you need to implement all of the sizes that are in use to have a crisp favicon on all browsers and displays.
If you are talking about the crispness in regards to a 16 x 16 icon, it comes down to skill designing it. The best way is to zoom in, select the pencil tool, and start editing those pixels. You could beef up the thin lines of the W that way.