Google Authenticator - Google Authenticator is a multifactor app for mobile devices.
Okta - Enterprise-grade identity management for all your apps, users & 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.
OneLogin - On-demand SSO, directory integration, user provisioning and more
UNLOQ - UNLOQ offers Multi-Factor Authentication, Transaction authorization, and Data Encryption solutions for Businesses and Organisations.
Auth0 - Auth0 is a program for people to get authentication and authorization services for their own business use.