GRUB - Multiboot boot loader
Apple - Available on iOS
Clover EFI bootloader - This is EFI-based bootloader for BIOS-based computers created as a replacement to EDK2/Duet...
iPad 9.7" - The new $329 entry-level iPad for students
U-Boot - Das U-Boot (the Universal Bootloader) and Embedded Linux
Microsoft Surface - Life is a passion project.