Gravity Forms placeholder plugin. Slightly modified from here: http://www.wpbeginner.com/wp-tutorials/how-to-add-placeholder-text-in-gravity-forms/

gforms-placeholder.php

/**
 * Add placeholder attributes to Gravity Form inputs.
 */

function my_standard_settings($position, $form_id) {
  if ($position == 25) : ?>
		<li class="admin_label_setting field_setting" style="display:list-item;">
			<label for="field_placeholder">Placeholder Text
				<a href="javascript:void(0);" class="tooltip tooltip_form_field_placeholder" tooltip="&lt;h6&gt;Placeholder&lt;/h6&gt;Enter the placeholder/default text for this field.">(?)</a>
			</label>
			<input type="text" id="field_placeholder" class="fieldwidth-3" size="35" onkeyup="SetFieldProperty('placeholder', this.value);">
		</li>
	<?php endif;
}

add_action('gform_field_standard_settings', 'my_standard_settings', 10, 2);

function my_gform_editor_js() { ?>
	<script>
		// binding to the load field settings event to initialize the checkbox
		jQuery(document).bind('gform_load_field_settings', function(event, field, form){
			jQuery('#field_placeholder').val(field['placeholder']);
		});
	</script>
<?php }

add_action('gform_editor_js', 'my_gform_editor_js');

function my_gform_enqueue_scripts($form, $is_ajax=false) { ?>
	<script>
		jQuery(function() {
			<?php foreach ($form['fields'] as $i=>$field) : ?>
				<?php if (isset($field['placeholder']) && ! empty($field['placeholder'])) : ?>
					jQuery('#input_<?php echo $form['id']?>_<?php echo $field['id']?>').attr('placeholder', '<?php echo $field['placeholder']?>');
				<?php endif; ?>
			<?php endforeach; ?>
		});
	</script>
<?php }

add_action('gform_enqueue_scripts', 'my_gform_enqueue_scripts', 10, 2);

Nevermind. This is a better solution: http://wordpress.org/extend/plugins/gravity-forms-placeholders/