Soovle - Soovle is a customizable search engine provides the search suggestion of the best provider on the net.
Google Trends - Explore Google trending search topics with Google Trends.
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.
Moz - Backed by industry-leading data and the largest community of SEOs on the planet, Moz builds tools that make inbound marketing easy.
Keyword Eye - Keyword Eye is a suite of visual keyword and competitor research tools.
Serpstat - Serpstat is the Swiss army knife for automating SEO processes. With a suite of powerful modules, you can track your performance, analyze your competitors, research keywords and backlinks, audit your website, and so much more.