Steambot by EGibbs87

This extension allows you to register steam games to your account in batches by entering them into the Steambot interface either piecewise or comma-delimited.

Steambot will help direct you to Steam's login page so that you don't need to bother trusting him with your credentials, as you do this on your own without his intervention. Once logged in, just add your keys to the interface, and Steambot will ensure that all of your games are claimed to be added to your Steam library!