Currently, I do not see a command using Tentacle.exe or octo.exe to unregister a tentacle.
We are having a problem with an autoscaling group. When a dead tentacle exists, the deployments take so long that it prevents a deployment from happening in a timely manner. The autoscaling group destroys the instance, and the problem compounds itself. After a few hours, you have an environment with 15-20 dead instances in it. I need a tentacle to unregister itself on shutdown.