Brian Alexander

Adds the current page’s template name to the admin bar.
Because this plugin reveals potentially sensitive information about the active theme, it is recommended for development environments only, and should not be enabled on a production site.

What Template

Adds the current page's template name to the admin bar.

Jakobodb

This utility plugin changes the theme of the current user to Sunrise, and uses the Sunrise color scheme when browsing the front-end, to help ensure you are viewing and editing the Development Site when making crucial changes to a site.
This plugin also adds a menu item to the admin bar to further confirm that you are on the Development Site.

Development Mode

Uses Sunrise theme on Dashboard and Frontend to visually represent development mode

What Template vs Development Mode