IDEs
Multi-Purpose: Visual Studio Code (free)
.NET / C#: Visual Studio (free)
Android App Dev: Android Studio (free)
Python: Pycharm (free)
Java: IntelliJ IDEA (free)
C / C++: CLion (free for students)
Git
GitKraken (free)
Sourcetree (free)
Fork (free unlimited evaluation)
Databases
Server: MySQL Server (free) or MongoDB (free)
Reading database: HeidiSQL (free) or Datagrip (free for students)
Designer: DB Designer (free)
Others
.NET Decompiler: dotPeek (free)
API-Testing: Postman (free)
Cheap VPS-hosting: GalaxyGate