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.
Google Trends - Explore Google trending search topics with Google Trends.
Moz Analytics - Moz Analytics is the most popular SEO (Search Engine Optimization) tool that uses both basic and advanced research tools to enhance your traffic.
Keywords Everywhere - Free browser add-on for keyword volume, CPC & competition
Keyword Eye - Keyword Eye is a suite of visual keyword and competitor research tools.
Serpstat - Search analytics, Rank tracking, Backlink analysis and Site Audit tool.