I found two awesome keyword tools last week:
KW Finder (kwfinder.com)
Enter keyword and receive detailed SEO analysis with a few clicks. This kind of tool would usually be sold for A LOT but the author (for some strange reason) offers it for free.
Keyword Tool (keywordtool.io)
This tool will go and scrape Google suggest, giving you lots of keywords ideas. There is a similar service, though not as well designed, called UberSuggest.