Dotnet
Command-line deobfuscator for common .NET protections (ConfuserEx, ILProtector, Goliath.NET, etc). It's not always magical ( sometimes you have the explore/understand the options) but it definitely helps.
To run it, open a Command Prompt and type:
de4dot
As of version 2023.05, retoolkit also includes a de4dot GUI.
Decompiler and debugger for .NET assemblies. I believe the best feature is the ability to edit and recompile code. It gives you full control of a .NET program.
Unpacker and logger for .NET programs.
.NET Assembly memory dumper with anti-dump bypass and injection capabilities.
Code browser and decompile for .NET. It's very up to date.
Assembly explorer for .NET assemblies. It has a powerful names, strings, and flow deobfuscator that assists with the deobfuscation of .NET protectors.