Affinity audiences list and the list of In-market audiences can be quickly browsed on this AdWords codes and formats page in the AdWords API documentation.
Although nothing extraordinary but this list could be very useful in some cases.
For example, you could be outside meeting a new prospect and suddenly if they want to consider the possibility of advertising on the display network, then, instead of loading the AdWords interface, the above page could be quickly loaded on your mobile, to easily see the list of available in-market audiences or the affinity audiences list.