In all likelihood, Google's unlocked Galaxy Nexus will be the first smartphone to come with Android 4.1 (otherwise known as "Jelly Bean") pre-installed. We believe this to be true because Google inadvertently tipped its hand in a Google Play listing for the Galaxy Nexus in which a product description touted it as the first "first phone with Android 4.1," a description that has since been removed.
The folks over at Droid-Life, who first reported the listing (as discovered by a user on XDA Developers forum), had the foresight to snag a screenshot before Google had a chance to cover its tracks, and once the Jelly Bean's out of the bag, there's no putting it back in.
If you pay attention to the wording, you'll notice Google says the Galaxy Nexus is the "first phone" to rock Jelly Bean, not necessarily the first device. As CNet notes, that leaves the door wide open for the Nexus 7-inch tablet, co-developed between Google and Asus, to swoop in as the very first gadget running Android 4.1.