Perhaps you’ve tried installing vSphere/ESXi via a remote console session from your Mac and have been stuck at the screen where you have to click F11 to accept the licensing agreement to move on.
By default on my 10.8.2 (Mountain Lion) Macbook Air when I use fn + F11 it would show my desktop, not send F11 thru to the console session. In order to change the behavior of F11 you may need to do the following:
Go to System Preferences – Mission Control
Change Show Desktop from F11 to some other key, I’ve used F13 in this example.
Now from your remote console session you should be able to use fn + F11.