I use Keyword Discovery. If you know what you want out of it and get a month long subscription, I would say it is work the money.
Google analytics, yes GA, because what a keyword tool shows and what you will discover from GA is so much more useful, it makes more sense.
I'm use Google keyword tool, then use SKCA ( Stealth Keyword Competition Analyser ).....pick the "amazing"..score, don't forget look to the sum of advertising (adwords).
The POLL is closed and the results are in with 154 votes for the most recent TopRank OMB Reader Poll: Best Keyword Research Tools. The two long standing tools of choice for many search marketers, Keyword Discovery and Wordtracker, battled it out and in the end, tied.
Considering that google is the primary search engine used they have better and mor in depth data to give you more accurate information
A great keyword tool that you can use for free but also has a paid version too is Market Samurai. It is pretty awesome for finding long tail keywords or just low competition keywords that will be easy to rank for. There are hundreds of how to videos for it online, and the makers have their own list of video tutorials also.
Totally agree with 'vimier' Market Samurai is used by a lot (I mean a lot) of Internet Marketers........and I have always rated it as an awesome tool for Keyword research!!
Google ad word is best tool for keyword search. all type of keywords can be find in Google ad word search if you have an account.