On a recent project I found myself using the following NuGet packages which made life a ton easier. Since, I’ve used pretty much all four of these packages on all of projects.

ControlzEx
Easy way to create Tooltip popups (like hovering over buttons). Great for informing users on how to use particular parts of your project.

MahApps.Metro
An easy way to style your application. Although it still look’s a bit outdated, it’s much better than the default C# style. A quick, easy way to make your project look modernish without needing an entire graphics team.

PrettyBin
An easy, effective way of cleaning up all libraries in to a single “bin folder”. Muchly needed for large projects that have a lot of files.

Tulpep.NotificationWindow
Made creating a tool tip pop up / notification pop up extremely easy. I created a function which I’d call when needed.