SARDU creates a multiboot USB drive, a multiboot DVD ISO or multiboot CD ISO (all-in-one) for free (personal and non commercial use, read the license). It is a freeware antivirus rescue disk application that's easy-to-use.
Here are some screenshots to illustrate the features and user interface of this application:
WinToUSB
WizTree
MeinPlatz
Rufus
Universal USB Installer