YubiKey - The YubiKey is a one-time password device for secure login with two-factor authentication
Google Authenticator - Google Authenticator is a multifactor app for mobile devices.
Nitrokey - Email Encryption. Encrypt your emails with GnuPG, OpenPGP, S/MIME or your favourite email client.
andOTP - andOTP is a two-factor authentication App for Android 4.4+
SoloKeys - Secure login made open and easy 🔒
Microsoft Authenticator - One app to quickly and securely verify your identity online, for all of your accounts.