There are a lot of bizarre cards in Battle for Zendikar. The obviously good cards like Gideon, Ally of Zendikar and Bring to Light have already seen significant price increases leading up to the sets release, but I have to imagine that a set with so many strange cards will have some sleepers.
A card that is generating some buzz despite being initially scoffed at is Oblivion Sower. The early disappointment was rooted in the idea what we were used to a six mana spell that won the game on its own in Elspeth, Sun's Champion. Now we know that we don't really have options like that, and Oblivion Sower does a great job at bridging the gap between doing kind of big things and drawing cards off of Hedron Archive and casting Ulamog.
Oblivion Sower could have been pre-ordered in the three dollar range, and it now slightly over five. This is indicative of an increase in demand, and some early success could lead to a $10+ price tag. Being in the duel deck will keep the price down long term, but this could be a great card to acquire for a quick flip before most players can get their hands on them.