There is no /usr/libexec/uucp/uucico in base; uucico (8) is provided by

the net/uccp package and is installed under /usr/local/. Since we don't
want a shell that default to /usr/local/..., use /sbin/nologin.
The uucp package will automatically change to the correct shell on
pkg_add / pkg_delete.
idea from and ok miod@

src/etc/master.passwd

@@ -14,7 +14,7 @@ _x11:*:35:35::0:0:X Server:/var/empty:/sbin/nologin
 _kdc:*:59:59::0:0:Kerberos Server:/var/empty:/sbin/nologin
 _kadmin:*:60:60::0:0:Kerberos Admin Server:/var/empty:/sbin/nologin
 _spamd:*:62:62::0:0:Spam Daemon:/var/empty:/sbin/nologin
-uucp:*:66:1::0:0:UNIX-to-UNIX Copy:/var/spool/uucppublic:/usr/libexec/uucp/uucico
+uucp:*:66:1::0:0:UNIX-to-UNIX Copy:/var/spool/uucppublic:/sbin/nologin
 www:*:67:67::0:0:HTTP Server:/var/www:/sbin/nologin
 _isakmpd:*:68:68::0:0:isakmpd privsep:/var/empty:/sbin/nologin
 named:*:70:70::0:0:BIND Name Service Daemon:/var/named:/sbin/nologin