The Guild Wars 2 API C/C++ Library Project provides methods for sending and receiving data from the Guild Wars 2 API's servers in C and C++. Methods for handling Items and Guilds are currently missing.
Steam has built out a global network over the years to ensure low latency, QoS, and protection from DoS attacks. A recent Steamworks SDK update allows Steam partners to access Steam's internal network so that the partners can leverage the same infrastructure that has made Steam resilient.
Games media service RAWG opens its API for developers. RAWG is the largest games database with over 300,000 of games, 2M of screenshots, 400K of reviews and ratings, and now you can access all of it and much more via the API. Access over 300,000 games, 2M of screenshots, and much more.