Aegis Authenticator - Aegis Authenticator is a free, secure and open source app to manage your 2-step verification tokens...
Authy - Best rated Two-Factor Authentication smartphone app for consumers, simplest 2fa Rest API for developers and a strong authentication platform for the enterprise.
Google Authenticator - Google Authenticator is a multifactor app for mobile devices.
Duo Security - Duo Security provides cloud-based two-factor authentication. Duo’s technology can be deployed to protect users, data, and applications from breaches, credential theft, and account takeover.
OTP Auth - The app for calculating one-time-passwords on iPhone and iPad.
privacyIDEA - privacyIDEA is an enterprise ready, open-source multi factor authentication system.