Back to the Previous Tab by Herman Streltsov

This extension gives you a handy way to switch back to the tab you were just looking at. Just hit Ctrl+6 (the one with the caret!) and you are right back on your previous tab.

Use cases

1. Think of it this way - you've got numerous tabs open for different tasks and you switch to a pinned tab to check an email or you followed some notification. After checking the email or notification, you can't find the tab you were on before. Sounds familiar? With this extention you can easily switch back to the previous tab you were viewing, maintaining your workflow without a hitch.
2. Or imagine you're reading an article in a foreign language on Tab A and using a dictionary on Tab B. This extension allows you to easily toggle back and forth between the two tabs.