Matthew Garrett
The Linux developer who wrote shim in 2012, the tiny first-stage loader that lets mainstream Linux distributions still boot on Secure Boot machines.
When Microsoft required Windows 8 PCs to ship with UEFI Secure Boot enabled, it looked for a while as if Linux would be locked out of ordinary hardware. Garrett, then at Red Hat, wrote shim: a minimal loader signed with Microsoft's key that in turn verifies the distribution's own GRUB and kernel against the distribution's keys. It was pragmatic rather than elegant, and it is still the standard approach.
Before that he had done a lot of power-management and ACPI work in the Linux kernel, and he has since written at length about TPMs, firmware and what you can actually trust in a computer. His blog is one of the few places where the boot chain is explained by someone who has both implemented it and been annoyed by it.