Google Keyword Research

Hello,

Here are some of the most popular tools I use the most when performing a typical technical SEO audit 

Screaming Frog
ISS SEO Toolkit
SEMrush Site Audit
Pingdom DNS Check
BuiltWith
Reverse IP Lookup
GTmetrix

Other Tools used by me are 

Google PageSpeed Insights - Check the speed and usability of your site on multiple devices
Keywordtool.io - 700+ keyword ideas based on a single keyword
Google Webmaster Tools + Bing Webmaster Tools - Constant website analysis, alerts, and error reports
Open Site Explorer - Comprehensive link analysis
Google Keyword Planner - Know what people search for
Google Trends - Changes in search volume for key terms
QuickSprout Website Analyzer - Full analysis of your website
SERPs Rank Checker - See where your site ranks for certain terms
SEO Site Checkup -Audit and score for your website