GrepWords - Grepwords is an API-first Google Keyword Suggestion Tool.
Keyword Country - Keyword Country is an AI-powered keyword research tool.
iSpionage - AdWords competitor keywords with the click of a button and monitor competitor PPC landing pages.
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 Tool Dominator - Keyword Tool Dominator is a keyword research tool to find long tail keywords.
Keyword Hero - Keyword Hero is an SEO tool for organic keywords.