MultiBoot USB
This is a collection of GRUB scripts that allows to create a bootable pendrive (USB dongle, flash stick) supporting a number of different OS images. Simply copy ISO files under `/iso-imgs`. Both UEFI and Legacy BIOS boot modes can be enabled simultaneously.
Rescatux is a GNU/Linux rescue cd (and eventually also Windows) but it is not like other rescue disks. Rescatux comes with Rescapp. Rescapp is a nice wizard that will guide you through your rescue tasks.