Create a pfSense box with Packer
As packer is not able to download gzipped ISO files directly, you have to download it manually and extract it. Then customize the pfsense.json file so packer could find the ISO file locally.
http://fleximus.org/mirror/pfsense/downloads/pfSense-LiveCD-2.1-RELEASE-i386.iso.gz
packer build -only=virtualbox-iso pfsense.json