Thunder Client is Rest API Client Extension for Visual Studio Code, with simple and clean design. The extension makes api testing very easy with Scriptless GUI based testing.
Recently went paid with a limit of 25 requests per collection on the free tier.
** BEWARE **
Several reviews have also pointed out it is deleting your collections and environments if you roll back to the previously free version. Happened to me as well.
The app is very good. Simple yet powerful. I would add one thing: the possibility to run a script before a request is sent; for example to retrieve some variable from a database.