1. Nested virtualization feature that it mean you can run Hyper-V inside of a Virtual Machine (VM). Hyper-V host can itself be virtualized and so very useful for testing purpose.
2. Shielded virtual machine, you can review this blog article too, the major concept to avoid VM steal:
http://www.alessandromazzanti.com/2017/03/windows-server-2016-deploying-shielded.html
3. Hot Adding Hyper-V Network Adapters and Memory without reboot necessity.
4. Cluster upgrade path from 2012 R2 to 2016 - If you have cluster nodes Windows 2012 R2 you can slowing upgrade to windows 2016 server mantaining cluster in mixed mode and finally using the command powershell (not revirsible)
Update-ClusterFunctionalLevel
4. Windows Server 2016 introduce Cluster Azure Cloud Witness too.
5. Site-aware Failover Clusters At the same time cluster groups server based on site geographical location.
Site-aware Failover Clusters in Windows Server 2016.
cluster-whiteness-cloud-configuration
Workgroup e Multi-domain Cluster on 2016 override 2012 R2 limitations that all cluster servers member need to be all located in same AD site.
6. Diagnostic in Failover Clustering is enhanced than in the past, you can review these articles:
Windows Server 2016 Failover Cluster Troubleshooting Enhancements – Cluster Log
Windows Server 2016 Failover Cluster Troubleshooting Enhancements – Active Dump
7. SMB Multichannel e Multi-NIC Cluster Network
https://technet.microsoft.com/en-us/windows-server-docs/failover-clustering/smb-multichannel
[Reference article]
https://www.backupassist.com/blog/news/what-to-look-forward-to-in-windows-server-2016/