Unregister all Core widgets

gistfile1.php

/**
 * Unregister Core Widgets
 *
 * Unregisters all core widgets based on their individual
 * class names.
 *
 * @uses unregister_widget() to unregister from the Widget Factory class
 */
function remove_core_widgets() {
	unregister_widget( 'WP_Widget_Calendar' );
	unregister_widget( 'WP_Widget_Pages' );
	unregister_widget( 'WP_Widget_Archives' );
	unregister_widget( 'WP_Widget_Links' );
	unregister_widget( 'WP_Widget_Meta' );
	unregister_widget( 'WP_Widget_Search' );
	unregister_widget( 'WP_Widget_Text' );
	unregister_widget( 'WP_Widget_Categories' );
	unregister_widget( 'WP_Widget_Recent_Posts' );
	unregister_widget( 'WP_Widget_Recent_Comments' );
	unregister_widget( 'WP_Widget_RSS' );
	unregister_widget( 'WP_Widget_Tag_Cloud' );
	unregister_widget( 'WP_Nav_Menu_Widget' );
}
add_action( 'widgets_init', 'remove_core_widgets' );

On a relatively vanilla site (maybe 3 plugins) unregistering the unneeded core widgets saved 6 queries on the homepage.