Wordtracker is a legacy keyword research tool launched in the United Kingdom in 1998, aggregating search terms from Google, YouTube, Amazon and more, with search trend and competitor keyword analysis.
LowFruits is a keyword opportunity finder from Semper Plugins (AIOSEO) that uses real SERP analysis to find "low-hanging fruit" long-tail keywords. The standard plan costs $20.75/month (yearly), with keyword clustering, rank tracking, and 150K low-authority domain data.
KWFinder is a low-cost keyword research tool launched by Mangools in 2015 in Slovakia, covering 2.5 billion+ keywords and 65,000+ city-level locations, with an entry price of $29/month for beginners and small teams.