They can attack anything a normal creature on the battlefield can attack
Other ideas that were too pricey for the deck include Defense of the Heart, Dust Bowl, Strip Mine, Pernicious Deed, Oblivion Stone, Expedition Map, Mirrorpool, Traverse the Ulvenwald, Attrition, and maybe Primeval Bounty
As such you can fairly reliably chunk planeswalkers for two in the mid game with a Predator which stops them from being cast or at least stops them doing much useful
Played fairly, the two-drop does offer some removal protection, but is that enough to beat out things like Dusk Legion Zealot and Gifted Aetherborn
But, if you have fans of Magic: The Gathering or The Lord of the Rings in your life, the Scene Boxes make great stocking stuffers