A new template pfSense SNMP is now available for out-of-the-box monitoring.
You can get this template:
templatesdirectory of the downloaded latest Zabbix version. Then, while in Configuration → Templates you can import them manually into Zabbix.
Native support for the items system.hw.chassis, system.hw.devices, vfs.dir.count and vfs.dir.size has been added to Zabbix agent 2. These items, used with Zabbix agent 2, now support concurrent check processing.