FreeOTP - Open source implementation of the two-factor authentication HOTP and TOTP schemes.
Aegis Authenticator - Aegis Authenticator is a free, secure and open source app to manage your 2-step verification tokens...
Google Authenticator - Google Authenticator is a multifactor app for mobile devices.
Authy - Best rated Two-Factor Authentication smartphone app for consumers, simplest 2fa Rest API for developers and a strong authentication platform for the enterprise.
SoundLogin - SoundLogin simplifies the login process for accounts protected by two-factor authentication
OTP Auth - The app for calculating one-time-passwords on iPhone and iPad.