CoreCLR is the runtime for .NET Core. It includes the garbage collector, JIT compiler, primitive data types and low-level classes.
Dapper - a simple object mapper for .Net
ShareX is a free and open source program that lets you capture or record any area of your screen and share it with a single press of a key. It also allows uploading images, text or other types of files to many supported destinations you can choose from.
A collection of awesome .NET core libraries, tools, frameworks and software
ScreenToGif allows you to record a selected area of your screen, edit and save it as a gif or video.
.NET Decompiler with support for PDB generation, ReadyToRun, Metadata (&more) - cross-platform!
EF Core is a modern object-database mapper for .NET. It supports LINQ queries, change tracking, updates, and schema migrations.
Mono open source ECMA CLI, C# and .NET implementation.
Google's Material Design in XAML & WPF, for C# & VB.Net.