Use the buttons
setting:
var buttons = ['formatting', '|', 'bold', 'italic'];
$('#redactor').redactor({buttons: buttons});
This is extract from documentation:
By default, this setting contains the following array of toolbar's
buttons:
['html', '|', 'formatting', '|', 'bold', 'italic', 'deleted', '|',
'unorderedlist', 'orderedlist', 'outdent', 'indent', '|',
'image', 'video', 'file', 'table', 'link', '|',
'fontcolor', 'backcolor', '|', 'alignment', '|', 'horizontalrule']
// additional buttons
// 'underline', 'alignleft', 'aligncenter', 'alignright', 'justify'
// If you wish to set your own array, set it in this option:
$('#redactor').redactor({
buttons: ['html', '|', 'formatting', '|', 'bold', 'italic']
});