depinit. written by richard lightman because he too did not trust the overcomplexity of sysv initscripts and wanted parallelism, it was adopted by linux from scratch and seriously considered for adoption in gentoo at the time. richard is extremely reclusive and his web site is now offline: you can get a copy of depinit however using archive.org.
using depinit in 2006 i had a boot to X11 on a 1ghz pentium in 17 seconds, and a shutdown time of under three. depinit has two types of services: one is the "legacy" service (supporting old style /etc/init.d/backgrounddaemon) and the other relied on stdin and stdout redirection. in depinit you can not only chain services together for their dependencies but also chain their *stdin and stout* _and_ stderr together.
that has some very interesting implications. for example: rather than have some stupid system which monitors /var/log/apache2/logfile for security alerts or /var/log/auth.log for sshd attacks, what you do is run sshd or apache2 as a *foreground* service outputting log messages to stderr, chained to a "security analysis" service which then chains to a log file service.
the "security analysis" service could then *immediately* check the output looking for unauthorised logins and *immediately* ban repeat offenders by blocking their IP address, rather than having to either poll the files (with associated delays and/or CPU untilisation) or have some insane complex monitoring of inodes which _still_ has associated delays.
also depinit catches *all* signals - not just a few - and allows services to be activated based on those signals. richard also had a break-in on one system, and they deployed the usual fork-and-continue trick, so he wrote some code which allowed the service-stopping code to up the agressiveness on hunting down and killing child processes. this also turned out to be very useful in cases where services went a bit awry.
basically the list of innovations that richard added to depinit is very very long, in what is actually an extremely small amount of code. i simply haven't the space to list them all, and no, richard was not a fan of network-manager either.
btw you might also want to look at the replacement for /bin/login that richard wrote. it was f****g awesome. basically what he did was use gpg key passphrases as the login credentials.... and ran gpg-agent automatically as part of the *login*. i have never even seen a PAM module which does this trick. it would be awesome to do the same trick for ssh as well.
it's fascinating what someone can get up to when they have the programming skill and the logical reasoning abilities to analyse existing systems that everyone else takes for granted, work out that those sytems are actually not up to scratch and can write their *own* replacements. it's just such a pity that nobody seems to have noticed what he achieved.