Program: WinAuth
License: Open Source/GPL
Description: An easy to use, portable 2FA client.
Website: https://winauth.com/
Other: Can be made portable rather easily by following the FAQ: https://winauth.com/faq/
"However, if you want to run WinAuth in true portable mode, or a USB stick for example, then you first need to copy the WinAuth.exe file onto your USB stick. Next, open Explorer and go to c:\Users\\AppData\Roaming\WinAuth (Windows 7/8.x) and copy or move the winauth.xml file from there into the same folder as winauth.exe on your USB stick. When you then run WinAuth from the USB stick it will run in portable mode and will not write any data to that computer. This means it can be taken and used anywhere."