Vierra Magen isn’t the only specialty shop that Microsoft Corporation has tapped to handle its intellectual property matters. In fact, 13 of the 25 firms the software giant turned to as outside IP counsel qualify as boutiques.

Two of those boutiques — Chicago’s Banner & Witcoff and Salt Lake City-based Workman Nydeg­ger — were retained by enough other Fortune 100 clients besides Microsoft to qualify for inclusion in our rankings of the IP firms used by the country’s biggest companies.