IsoBuster Pro V2.6 Final Portable Full Version EXCLUSIVE

Best way I find to make IrfanView portable-friendly is to run a PC-installed version (with Plugins), go to Properties/Settings, under Extensions 'Clear all', then uncheck any 'Shell options'. Then copy the whole IrfanView folder to your USB drive. After doing that, re-enable the extensions and shell options on the install PC. I just drag-and-drop images into an open instance since there won't be file associations on the host machine.

IsoBuster Pro V2.6 Final Portable Full Version

The normal version if portable enough, the new machine doesn't know to call the program if someone clicks on a picture - because guess what - it hasn't been associated with that program. But that's not the programs fault, there is no reason to use a separate launcher.