KeywordTool.io - KeywordTool.io is the best FREE alternative to Google Keyword Planner and Ubersuggest. It uses Google's autocomplete feature to get over 750+ long-tail keywords for any given query.
Soovle - Soovle is a customizable search engine provides the search suggestion of the best provider on the net.
Keyword Surfer - Get search volumes & keyword data directly in Google.
Google Trends - Explore Google trending search topics with Google Trends.
Keyword Explorer by Moz - Find the best keywords to improve your website's SEO traffic
Keywords Everywhere - Free browser add-on for keyword volume, CPC & competition