Apache


 * [Hide Apache Header Information](http://www.serverschool.com/server-security/how-to-hide-apache-header-information/) - Apache tells the world about the operating system, the modules, and the version currently running. This can be a big target for attackers that lets them know what version to try.
 * Better yet though, you can set your own silly strings there instead.
 * Security through Obscurity is nothing safe though.