Interesting results, it seems there isn't a universally approved answer.
I was completely unaware that people used /sbin/nologin for this, probably because I just looked at what Ubuntu does and copied that.
To the people that use nologin as root shell, how do you deal with the inability to use "sudo su", "sudo -s" or "sudo -i" to spawn a root shell? Do you just never do that, using "sudo" for everything, or do you launch the shell with "sudo bash" or even "sudo bash -l"?