After installing open-vm-tools, ESXi reported that VMware Tools were Installed and running on the Debian 8 guest. However any attempt to gracefully power off the guest within ESXi would fail with these errors:
[msg.tools.haltFailed] The request to Power off this virtual machine failed because the corresponding VMware Tools script did not run successfully.
Also present in the logs was this error:
msg.tools.poweronFailed] The VMware Tools power-on script did not run successfully in this virtual machine. If you have configured a custom power-on script in this virtual machine, make sure that it contains no errors.
For this scenario, the solution was to first uninstall open-vm-tools. For Debian / Ubuntu:
sudo apt-get remove open-vm-tools
then install open-vm-tools-desktop
sudo apt-get update
sudo apt-get install open-vm-tools-desktop
You should then be able to power off and power on the guest within ESXi.