Here's a tree that sneaks up on you when you're not looking and smacks you in the back of the head.
The script uses smallg's useful PlayerLooking function to determine whether or not the player can see the tree (I'm not sure if GG has an equivalent function, but smallg's works well so I'll stick with that).
I haven't included the sounds, which come from freesfx.co.uk - whichever sounds you choose, name them rustle.ogg and swish.ogg and put them in the audiobank/misc folder.
Once you've unzipped the .zip file, you can drop the included 'files' folder into your GameGuru folder, as I've maintained the correct folder structure. If you want to move the script to another location (it's in scripts/Gtox scripts), remember to change the script path in the fpe.
Here is the link - https://www.dropbox.com/s/uvi30k21yvnkd2f/sneaky%20tree.zip?dl=0