Market Samurai without a doubt.

Keyword Analysis Tool - Market Samurai

You can not go wrong with Market Samurai, but my personal preference is Keyword Scout. Also don't forget there is so much you can learn from a free Google Adwords Keyword tool.

Another vote here for Market Samurai. Many claim to be the best, while it just delivers.

I find Wordtracker to be the best.

They were always the best before MS and with their recent upgrades they're back to number 1 I think.

keyword research tools for SEO, PPC, link building and blogging | Wordtracker

True, Market Samurai and Google Keyword Tool rocks, but you also need to use your head as your tool to brainstorm and write down all potential keywords and other obscure keywords that you can use which will bring you traffic. It's good to use these tools but the main tool to find a profitable keywords is how much you understand and differintiate a buyer keywords to a general keywords.

Thesaurus and Dictionary is good to use for keyword replacement.

What about Jaaxy? I was told they are the best of the best today and at the best price in the market, a feat none can come near!

Besides WordTracker and Google Adwords Keyword Tool - you may to look into "google search suggestions".

These are the keywords that are shown as dropdown suggestions when you start typing into Google search box.

I use:

Google Keyword Tool - to get my categories and broad content ideas
Keyword Optimizer Pro - or any other Google related searches scraper to get my long tail content ideas and keywords.

Hasn't failed me yet!

I've also tried Traffic Travis, Market Samurai, Micro Niche Finder (ugh, I really don't like MNF) and those 2 tools have proven time and time again to be all I need.

Kindly,
- Stephen

For the keyword search tools, I usually used Google Adword Keyword Tool because it can provide you the global monthly, local monthly and the competition of the selected keyword phrases.