It took me a while to figure this out, but it’s quite simple.  If you want to skip all of the filters a Rails controller will run, simply put the following at the top of your controller:

skip_filter filter_chain #both documented in the Rails API

For example, if your application controller defines a filter to check if a user is logged in, it makes sense that this filter might run for all controllers, except in rare cases.  In my case, I have a dynamic image controller that doesn’t require all of the overhead that most controllers do.  For that controller, I use the above to skip all of the filters.