1. Google AdWords Editor

This neat application allows you to make changes in your AdWords account without being logged in. It's great to use when you don't have a connection (on a plane, for example). It also makes some AdWords-related tasks easier than doing them directly in the interface.
Here are some of my favorites:

• Move campaign elements. Easily move campaigns, ad groups, keywords and ads using AdWords Editor. The copy-and-paste process isn't exactly intuitive in Editor; but, once you get the hang of it, it's fairly straightforward and worth its weight in gold.
• Import and export elements. This is one of the easiest and fastest ways to export elements to Yahoo! or MSN without paying for third-party software.
• Find-and-replace function (plus other append tools). This tool makes it easy to make bulk adjustments to keywords, ad copy or URL information.
• Find spelling mistakes. Editor shows the red squiggly lines under misspelled or suspicious-looking words (similar to MS Word). Note: The AdWords interface doesn't catch spelling errors when you're creating ads directly in the interface.
• Find duplicate keywords. When accounts get large, it can be tough to remember if you've used a keyword before. So, you can use this tool to avoid redundancy.