UniMerge (Paid)

UniRx

Reactive Extensions for Unity

Consolation

In-game debug console for Unity.

SnazzyGrid (Paid)

Makes it easy to manage positions of assets in the scene with easy to use snapping tools and many more features to improve the scene creation workflow

GitHub for Unity

The new GitHub for Unity extension brings the GitHub workflow and more to Unity, providing support for large files with Git LFS and file locking