Using wp_parse_args to set up Plugin Default Settings

Try:

function eddslider_options_each( $key ) {

    $edd_slider_options = get_option( 'eddslider_options' );

     /* Define the array of defaults */ 
    $defaults = array(
        'slider_insert'     => 0,
        'slider_arrows'     => 0,
        'slider_bullets'    => 0,
        'slider_effect'     => 'fade',
        'slider_theme'      => 'default'
    );

    $edd_slider_options = wp_parse_args( $edd_slider_options, $defaults );

    if( isset($edd_slider_options[$key]) )
         return $edd_slider_options[$key];

    return false;
}