It's a powerful keyword research tool that I've used and am very impressed with.
Free Keyword Tool for Amazon, Google, YouTube, eBay, Etsy, Walmart, and Bing search.
Find long tail keywords with low SEO difficulty
Keyword Planner helps you research keywords for your Search campaigns. You can use this free tool to discover new keywords related to your business.
Use the latest Google search data to provide accurate and targeted advertising
Batch query Google keyword search volume, the feature is: batch query, free
A keyword research tool that generates thousands of profitable keywords with monthly search volume, CPC & competition