Libreboot - Libreboot is a distribution of ...
GRUB - Multiboot boot loader
PLoP Boot Manager - The PLoP Boot Manager is a small program to boot different operating systems.
Clover EFI bootloader - This is EFI-based bootloader for BIOS-based computers created as a replacement to EDK2/Duet...
Apple - Available on iOS
Bootice - Download Bootice - Edit your computer's MBR and PBR settings with various built-in tools such as a partition manager, UEFI editor, BCD configurator, and more