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.
Keyword Discovery - Keyword Discovery is a keyword research and analysis tool.
SECockpit - SECockpit is a keyword research and SEO management tool.
GrepWords - Grepwords is an API-first Google Keyword Suggestion Tool.
Serpstat - Search analytics, Rank tracking, Backlink analysis and Site Audit tool.
iSpionage - AdWords competitor keywords with the click of a button and monitor competitor PPC landing pages.