Okta - Enterprise-grade identity management for all your apps, users & devices
Aegis Authenticator - Aegis Authenticator is a free, secure and open source app to manage your 2-step verification tokens...
Auth0 - Auth0 is a program for people to get authentication and authorization services for their own business use.
Authy - Best rated Two-Factor Authentication smartphone app for consumers, simplest 2fa Rest API for developers and a strong authentication platform for the enterprise.
OneLogin - On-demand SSO, directory integration, user provisioning and more
OTP Auth - The app for calculating one-time-passwords on iPhone and iPad.