For example, pre-ordering from Amazon will earn you Batman (for use in a two-on-two arena battle mode) and an exclusive in-game item, the Amazonian Gauntlets (get it?). Walmart pre-orders also come with the arena mode Batman character, plus Joker's Trick Pistol. There are unique DC Comics-inspired armaments available from eight different retailers in all.
In addition, pre-ordering the collector's edition will entitle you to a Batman figurine and two more weapons. You can browse all the available options at SOE's pre-order site. And if you can't wait for your pre-ordered copy to arrive, sign up for the open beta now.