This is a language file I created for editing Cisco ASA/PIX firewall configs. It's very helpful. It would be nice to get this included in future releases. Many thanks.

<?xml version="1.0" encoding="UTF-8"?>
<!--

 Author: Simon Raiford <sraiford@gmail.com>
 This is a GTKSourceView language template for Cisco
 ASA and PIX firewalls. Feel free to update or redistribute 
 as you deem fit.

-->
<language id="cisco-firewall" _name="Cisco PIX/ASA" version="2.0" _section="Cisco">
  <metadata>
    <property name="mimetypes">text/plain</property>
    <property name="globs">*.txt;</property>
    <property name="comment-start">!</property>
  </metadata>
  <styles>
    <style id="comment" _name="Comment" map-to="def:comment"/>
    <style id="identifier" _name="Interface" map-to="def:keyword"/>
    <style id="access-list" _name="Access List" map-to="def:preprocessor"/>
    <style id="static" _name="Static" map-to="def:string"/>
    <style id="nat" _name="NAT" map-to="def:type"/>
    <style id="route" _name="Route" map-to="def:preprocessor"/>
    <style id="number" _name="Number" map-to="def:comment"/>
  </styles>
  <definitions>
    <context id="comment" style-ref="comment" end-at-line-end="true">
      <start>!</start>
    </context>
    <context id="description" style-ref="comment" end-at-line-end="true">
      <start>description</start>
    </context>

    <context id="hostname" end-at-line-end="true" extend-parent="false" style-ref="identifier">
      <start>hostname</start>
    </context>
    <context id="ip-address" end-at-line-end="true" extend-parent="false" style-ref="identifier">
      <start>ip address</start>
    </context>
    <context id="interface" end-at-line-end="true" extend-parent="false" style-ref="identifier">
      <start>interface</start>
    </context>
    <context id="policy-map" end-at-line-end="true" extend-parent="false" style-ref="identifier">
      <start>policy-map</start>
    </context>
    <context id="class-map" end-at-line-end="true" extend-parent="false" style-ref="identifier">
      <start>class-map</start>
    </context>

    <context id="access-list" end-at-line-end="true" extend-parent="false" style-ref="access-list">
      <start>access-list</start>
    </context>

    <context id="access-group" end-at-line-end="true" extend-parent="false" style-ref="access-list">
      <start>access-group</start>
    </context>

    <context id="static" end-at-line-end="true" extend-parent="false" style-ref="static">
      <start>static</start>
    </context>

    <context id="nat" end-at-line-end="true" extend-parent="false" style-ref="nat">
      <start>nat</start>
    </context>

    <context id="route" end-at-line-end="true" extend-parent="false" style-ref="route">
      <start>route</start>
    </context>

    <context id="number" style-ref="number">
      <match>(\b[0-9]+(\.[0-9]+)?|\.[0-9]+)([Ee][\+-]?[0-9]+)?\b</match>
    </context>
    <context id="cisco-firewall">
      <include>
        <context ref="comment"/>
        <context ref="description"/>
        <context ref="ip-address"/>
        <context ref="hostname"/>
        <context ref="interface"/>
        <context ref="policy-map"/>
        <context ref="class-map"/>
        <context ref="access-list"/>
        <context ref="access-group"/>
        <context ref="static"/>
        <context ref="nat"/>
        <context ref="route"/>
        <context ref="number"/>
       </include>
    </context>
  </definitions>
</language>