wokamoto

This plugin modifies RSS feeds and ATOM feeds as you want.
<h4>How to use</h4>
Putting the following templates into the current theme folder, then you can use the customized feed templates instead of the default ones.
<ul>
<li>feed-atom.php – Atom Feed Template for displaying Atom Posts feed.</li>
<li>feed-atom-comments.php – Atom Feed Template for displaying Atom Comments feed.</li>
<li>feed-rdf.php – RSS 1 RDF Feed Template for displaying RSS 1 Posts feed.</li>
<li>feed-rss.php – RSS 0.92 Feed Template for displaying RSS 0.92 Posts feed.</li>
<li>feed-rss2.php – RSS2 Feed Template for displaying RSS2 Posts feed.</li>
<li>feed-rss2-comments.php – RSS2 Feed Template for displaying RSS2 Comments feed.</li>
</ul>
Note: 
When these feed templates are not in the current theme folder, WordPress’s default feed templates will be used.

Feed Template Customize

This plugin modifies RSS feeds and ATOM feeds as you want.

tcloninger

Provides a custom error, using wp_die(), when any type of feed is attempted.
Feature Overview
<ul>
<li>Removal of ALL feeds</li>
<li>Allows for private (more secure) blogs</li>
<li>Works great with the “Private WP” plugin (requires login to view blog)</li>
</ul>
Important Notes
This is my very first plugin. I found it /very/ strange that nobody had done this.

FeedDisabler Plugin

Disables all feeds (rdf, rss, rss2, atom).

Feed Template Customize vs FeedDisabler Plugin