GRUB - Multiboot boot loader
Clover EFI bootloader - This is EFI-based bootloader for BIOS-based computers created as a replacement to EDK2/Duet...
U-Boot - Das U-Boot (the Universal Bootloader) and Embedded Linux
Grub2Win - Safely dual boot Windows and Linux without touching the Windows MBR.
Apple - Available on iOS
EasyBCD - EasyBCD is NeoSmart Technologies multiple award-winning answer to tweaking Windows bootloader.