I like / use:
https://www.tableau.com/ (for data),
https://www.emailhippo.com/ for list cleaning,
https://www.surveygizmo.com/ (surveys),
https://www.salesmessage.com/ (2 way SMS conversations),
https://baymard.com/products/studies (Ecommerce Research Studies like Checkout flow etc),
https://builtwith.com/ (tech data across the web),
https://www.shiftyjelly.com/pocketcasts/ (changed how I listen to podcasts in a GREAT way. They have a mobile and desktop and web based apps that all sync. They remove silent parts in podcasts. Worth the paid version)
Moved to https://www.mozilla.org/en-US/firefox/new/ from Chrome after 5+ years in chrome and glad I did)
To learn about pagespeed https://varvy.com/
A better search for your site and other data https://www.algolia.com/ (someone who performs a search on an ecommerce is a 10x better customer so worth spending that on the search result page pixel ;)) Also allows for a great search experience on a site like https://hn.algolia.com/?query=checklist&sort=byPopularity…
Clean URLs (an open source project) https://wistia.com/blog/fresh-url so your UTM links do not get passed around and people are more likely to share and competitors are not aware what you are doing
https://www.spyfu.com/ for all paid spend
https://www.usefomo.com/ (I like this better than Proof and they also recently launched an ad marketplace that I believe is a huge arbitrage for now…figure that most do not read this far down a thread 
AI Email Subject lines: https://phrasee.co/ (I am on their list and they do something with every subject line that is worth paying attention to 
?… they are getting massive amounts of data and putting it to use…
WordPress https://premium.wpmudev.org/
A better forum experience https://www.discourse.org/ that is open source and mobile friendly
https://www.wealthfront.com/ for investing
Personal Credit https://www.creditkarma.com/ (free credit reports and scores with a beautiful interface)
Weather App https://www.wunderground.com/
Word Clouds http://tagcrowd.com/ (I use this to make sense of large data sets quickly by dumping in the words/data and look for things that pop out like customer support inquiries, email subject lines etc)
Understand your visual heatmap and eye tracking http://solutions.3m.com/wps/portal/3M/en_US/VAS_NA/Home/ (they have a free trial and is by 3M with lots of research behind the tool) You can see the one I did for IMScalable awhile back
For DMARC a great free service (the paid is good also) https://www.fraudmarc.com/
https://www.cloudflare.com/ is one that many are using already but worth it. The new ARGO service is great.
1.1.1.1. from cloudflare for own DNS (i have used googles public DNS for years until this came out and switched) https://www.cloudflare.com/learning/dns/what-is-1.1.1.1/ is great and takes less than 3 minutes and your web experience will be better because of less latency (the real issue with web browsing – see why they have ARGO as a service now)
https://mxtoolbox.com/ for Email Delivery and Blacklist and many more things. The free version is great but I carry a paid account for clients that has a few extra bells and whistles.
https://cloudinary.com/ for image storage and manipulation
https://www.pixelz.com/ for Image retouching. Best for eCommerce type images where the background or color needs to be multiplied across on item with several variations