Some other tools that I consider to be vital for use in SEO they fill in a niche you won't find on any other the other categories. Ranging from Content Delivery network to a sitemap XML generator and a little tool that pings various crawl bots that you have updated your website content all in all these tools should give you an extra edge when it comes to SEO.
- Cloudflare: CloudFlare
My favorite CDN it will greatly help SEO and speed of your website loading times and improve your overall SEO score. Easy to use and free with a lot of options with most of them being a couple of clicks.
- Small SEO Tools: 100% Free SEO Tools - SmallSEOTools.com
An SEO swiss army knife this site provides some great free tools that basically covers every category in this article an absolute overdose of tools however you might some not as great a specific tools previously mentioned.
- SERP Simulator: SERP Simulator - SEO Title & Meta Description Tool 2018 | SERPsim
See how your the microdata markup of your website translates into a visual representation.
- Ping-o-Matic: Ping-o-Matic!
Notify a wide range of search engines and websites that you have updated the content of your website.
- XML Sitemap Generator: Create your Google Sitemap Online - XML Sitemaps Generator
Everything you need to generate an XML sitemap that you can then submit to the various search engines.