The Sphero .NET Windows SDK by Sphero allows developers to integrate robotic functionalities into Windows applications. Capabilities include to roll around, change colors, and run programs in addition to stream sensor, use the user interface elements, and drive Sphero.
Battlefield Bad Company is a first person shooter for Playstation 3 and Xbox 360. It keeps an amazing amount of statistics about its players, including a score, levels, a kill count, and many other things. The bfbcs.com site has a good listing of these, in a moderately accessible format. It also offers the Battlefield Bad Company Stats API, so programmers can add this functionality to their applications.
Riot Games senior software engineer Leigh Estes has published a three part series regarding the company's ongoing digital transformation to a microservices-driven software infrastructure. The company's journey involves some of the most textbook business and technical justifications for doing APIs.