A detailed list and a guide to the TinyMCE can be found here.

Functions File

/*-------------------------------------
	Custom WYSIWYG Styles
---------------------------------------*/
function acc_custom_styles($buttons) {
	array_unshift($buttons, 'styleselect');
	return $buttons;
}
add_filter('mce_buttons_2', 'acc_custom_styles');
/*
* Callback function to filter the MCE settings
*/

function my_mce_before_init_insert_formats( $init_array ) {  

// Define the style_formats array

	$style_formats = array(  
		// Each array child is a format with it's own settings
		array(  
			'title' => 'Big Red Text',  
			'inline' => 'span',  
			'classes' => 'big-red-text',
			'wrapper' => true,
			
		)
	);  
	// Insert the array, JSON ENCODED, into 'style_formats'
	$init_array['style_formats'] = json_encode( $style_formats );  
	
	return $init_array;  
  
} 
// Attach callback to 'tiny_mce_before_init' 
add_filter( 'tiny_mce_before_init', 'my_mce_before_init_insert_formats' ); 
// Add styles to WYSIWYG in your theme's editor-style.css file
function my_theme_add_editor_styles() {
    add_editor_style( 'editor-style.css' );
}
add_action( 'init', 'my_theme_add_editor_styles' );

css

.big-red-text {
	color: #E60000;
	font-size: 40px;
}