#1. SEMrush (24 votes) [Free 30 Day Trial]
#2. Ahrefs (22 votes) [7-Day Trial]
#3. Accuranker (6 votes) [Free 14 Day Trial]
#4. Google Search Console and Moz (5 votes) [Free 30-Day Trial]
#5. Advanced Web Ranking (4 votes)
#6. STAT and Agency Analytics (3 votes)
#7. SEOmonitor and SERPROBOT (2 votes)
Honorable mentions (1 vote): Authority Labs, SERPWoo, Pro Rank Tracker, SERPWatcher, Conductor, BrightEdge, SEO Powersuite, Microsite Masters, PlacesScout and SmallSEOTools.
Note: SEMrush was also voted the #1 keyword research tool by 133 SEO practitioners.