Hey clickbang,
Are you doing your keyword research for:
1) SEO for your webpages/website? (Wordtracker is good, keyword elite and seo elite work good too, I believe, but I've never used these 2, also there is the trellian keyword tool)
2) A pay per click (PPC) campaign using google adwords, yahoo search marketing etc? (e.g. Adwords keyword tool by google, adwords analyzer etc.)
3) For spying on competitors doing PPC (e.g. to "steal" their keywords and ads) - I believe Undercover Profits; Zamdoo.c0m, and SpyFu are some tools that help you with this.
4) Assessing demand for the keywords in a niche so that you can prep content off-site e.g. write keyword rich articles and post to ezine directories or to create keyword rich blogger pages with back links to your sales website etc.? (Back to Wordtracker for this one, I guess)
If I understand it correctly, the approach toward keyword research and the actual keyword tools that you would use, might be different, depending on the purpose of your research.
Would love to hear what you and the other members think about all this, as well as any of your experiences with other keyword research tools (I'm sure there are tons of others that I don't know about or have never heard of

).
Cheerio