My favorite *nix tool for firewalls is by far Firewall Builder 2.0. The latest revision of this great tool has been completely rewritten to use QT 3 for the gui API replacing GTK. This tool allows you to organize interfaces,networks,rules,policies and more into objects and templates which can easily be reused to create new firewalls or modify existing ones with ease. Firewall builder then creates the ruleset for the platform you require and supports all my favorites. (iptables,ipchains,ipfilter,pf,pix,and even custom linksys firmware!) FWB even checks all your rules for rule shadowing and other configuration errors and will then produce a script to install the new firewall and will connect via SSH to the target machine (which of course does not require X) and install the new firewall for you. This is easily the most kick ass firewall tool I am aware of and I reccomend anyone who is involved in building or maintaining firewalls (or anyone who would like to learn, the scripts provide an excellent way to study the diffrent rulesets) check this tool out. It is of course a sourceforge project.

http://www.fwbuilder.org/