The "Zellers" games on the 2600 had some hilarious label art. My favourite is Challenge:
Here's the label. So... this is a pirate of Ghostbusters right?
And here's the game itself. What the fuck? I control a duck?
The rest of the Zellers labels are also pretty funny, though most of them at least have something on the label that relates them to the game itself.
Here's another good one, Earth Attack. Yet another hilarious attempt at an all-in-one label that could be for basically anything:
--Zero