Can Ass Whuppin' be used to target a permanent in your own game?
Yes, you can see your own game, and Ass Whuppin' makes no limitation on which game its target has to be in, so you can target cards in your own game. This is necessary to be able to use the card at all in a silver-bordered game when nobody around you is playing another silver-bordered game.
That being said, the whole point of Ass Whuppin', and indeed all Un-sets, is to mess with the rules of the game and have a good laugh about it. If you can mess with other games through Ass Whuppin', but you are looking to powerplay in your own game, you're probably doing it wrong.