There's so much in IOS that it's easy to miss some of the less used commands. Why Cisco doesn't make a big deal out of these kinds of things I don't know. Sometimes it seems like they are all about Voice. Still, it would be nice to have an insider perspective on all the little tips and tricks you can do with IOS.
Configuration replacement command. Allows you to completely replace the running config. That's nice instead of having it load snippets or merging a config.
http://www.ciscoblog.com/archives/2007/03/configuration_r.html