Create multiboot live Linux on a USB disk...
Floppy Bird (OS)
A bash program to securely create a bootable USB device from one image ...
Create an ultimate multiboot USB flash drive with Grub2 bootloader
Create a bootable disk
Documentation Hiren's BootCD
Flappy Bird as bootable UEFI executable
An elementary OS app
A full brainfuck to bootable OS image compiler.