Well, assuming one is just trying to better optimize for the right keywords on a page, I've found Good Keywords (www.goodkeywords.com) to be a pretty helpful tool - it basically just pulls the data from Overture/Yahoo, so it's nothing super special, but it's pretty easy to use, free, and has a few other helpful features to help you do some on-page SEO. Hope this helps!
I use 'Good Keywords', as well, in conjunction with the AdWords Keyword Tool - this combination provides a pretty good list of keywords, based on the major SEs. I then use the AdWords Traffic Estimator to determine what advertisers are bidding for the keywords. This process has worked pretty well for me in setting up my sites. Sam
I'm use google adwords keyword tools for word analysis. I think it's easy for all of SEO specialists to use Google adwords. Google adwords is good SEO tools
GAK tools is enough but you need another ssoftware that is your brain to understand the seo competition level of that keyword
Google keyword tool is the best for keyword suggestions. I always use that in and it works perfectly and it give very accurate results.
I have been using Google's Keyword Tools and Keyword Elite and others, but the very best keyword tool out there (in my opinion) is Site Build It's Brainstormer & Keyword Researcher, which is included in their online business building service.
Market Samurai is a good one that is free for the seo tools so is traffic travis if you are tired at looking at just google keyword tool. The Market Samurai also has a large video library to explain SEO and how samurai works with it.
AdWords Keyword Tool may now be more accurate. I always use adwords keyword tool for my keyword research.
Google Keyword Tool - FREE Market Samurai - PAID Imho the best 2 tools, 1 free and 1 has a cost (but well worth it)