Its rare that anyone uses Gedit for ColdFusion, but hey, I know one that does! First off I use Gedit because its quick, simple, and super extensible. I work in ColdFusion equally as much as PHP as far as the serverside goes, so I like a pretty consistent environment for both, which this editor also provides. Not to mention I work on Linux, OSX, and Windows platforms.
First and foremost, if you're looking to use Gedit to edit coldfusion you need to add a language file for some syntax highlighting. This isn't hard at all, just a matter of grabbing the file. Here is a pretty good syntax file for ColdFusion (which I contributed some nice additions). You may also need to add the mimetype file if your system doesn't already recognize cfm and cfc files.
Now that you are up and running with cfm files, you're hungry for some snippets. You can get the ColdFusion Snippets on Github. From there you can upload them in the snippet manager or drop them into your ~/gnome2/gedit/snippets directory.
I don't have all the tags and functions, mostly just tags. It's really helpful for tags with required options, like cfloop, cfoutput, cfqueryparam which it will do a code completion dropdown with all valid cfsqltype options (cf_sql_varchar, cf_sql_integer, etc..). Its worth taking a look at! Enjoy!