Fun to do, maybe, but not real funny when you are the one getting ganked. Generally all you can do is try to run (you might make it), or bend over and take it like a whelp.
By the way, among hardcore PvPers ganking is considered vulgar and the lowest form of PvP. Many will simply refuse to do it, letting the low-level player walk away as beneath their notice.
If you are a low-level player, you might wanna hang back a second and make sure that end-game geared player looking at you is actually hostile. It may save you a death and a long walk home.