Ahrefs

I could have put this in the ‘espionage’ category as well. When you’re focused on getting to the top of the first page for a certain search phrase, you know who you’re trying to outrank. With Ahrefs, you can reverse engineer what they’ve done to get to the top of the results, then either duplicate it or do what they did but better, so that you can knock them down a notch and take over.