User Reference field with full list of users, but with current user as default selected value
Using hook_form_alter():

function example_form_alter(&amp;$form, &amp;$form_state, $form_id) {
    global $user;
    if ($form_id === 'my_form') {
        $form['field_user']['#default_value'] = array($user-&gt;uid =&gt; $user-&gt;name);
    }
}


Not tested, but it's the idea.