NetBSD has their new npf firewall which is quite nice. Of all the options their internal architecture is the cleanest. It gets less fanfare than the others because it has less drivers, although even that is partially due to a commitment against binary blobs.

FreeBSD is more practical but for example you find the config files scattered about the file system whereas in NetBSD they’re always exactly where I expect. SDF.org has a great NetBSD system if anyone wants to try it out.