What do you use to find profitable keywords?

Don't get me wrong, as so many IMers i know Keyword Elite, Market Samurai, Micro Niche finder and i know how to use them. Keyword research is like a hobby to me, i think its very exciting.

The problem is more How to actually find a promising keyword.

Example using Market Samurai, which is my favorite tool at the moment.

Let's take an example niche and keyword, "Acne"

There might (or might not) a related keyword to acne which is still "undiscovered" and it might have a very high search volume and a low count of existing pages in Google.

If i feed "acne" into MS, it might spit out a list of 200-300 keywords, like
"acne scar", "acne removal", "acne cream", "acne products" etc. etc.

Now..its likely i don't see a promising keyword after i did the analysis, and i have to re-brainstorm and feed new, related keywords...eg. i could feed it a related start keyword like "clear skin".

Again, who knows, the resulting list might contain a goldmine keyword.

But the goldmine could as well only appear when i feed Market Samurai "get rid of pimple" etc.... All keywords which are somewhat related.

I always end up trying and trying, enter a related keyword, get 300 results, analysis, try another bunch of keywords.

Is there a way or a tool which allows such brainstorming to come up with a WIDE array of related keywords. Not only limited to 300 keywords based on one single seed keyword - but maybe thousands and then do an analysis of that much larger list to find a potential good keyword?