I think Cosmopolitan[1] is a beautiful example for self-modifying executables.
> Cosmopolitan Libc makes C a build-once run-anywhere language, like Java, except it doesn't need an interpreter or virtual machine. Instead, it reconfigures stock GCC and Clang to output a POSIX-approved polyglot format that runs natively on Linux + Mac + Windows + FreeBSD + OpenBSD + NetBSD + BIOS with the best possible performance and the tiniest footprint imaginable.
> Please note that your APE binary will assimilate itself as a conventional resident of your platform after the first run, so it can be fast and efficient for subsequent executions.
> Cosmopolitan Libc makes C a build-once run-anywhere language, like Java, except it doesn't need an interpreter or virtual machine. Instead, it reconfigures stock GCC and Clang to output a POSIX-approved polyglot format that runs natively on Linux + Mac + Windows + FreeBSD + OpenBSD + NetBSD + BIOS with the best possible performance and the tiniest footprint imaginable.
> Please note that your APE binary will assimilate itself as a conventional resident of your platform after the first run, so it can be fast and efficient for subsequent executions.
[1] https://github.com/jart/cosmopolitan