Aegis Authenticator - Aegis Authenticator is a free, secure and open source app to manage your 2-step verification tokens...
andOTP - andOTP is a two-factor authentication App for Android 4.4+
Authenticator - Authenticator is a simple, free, and open source two-factor authentication app.
OTP Auth - The app for calculating one-time-passwords on iPhone and iPad.
Authenticator Plus - Authenticator Plus generates 2-step verification codes and lets you synchronize your accounts.
Tofu Authenticator - Tofu Authenticator is an open-source easy to use two-factor authentication app that lets you secure your accounts with one-time passwords.