Walter White tells drug kingpin "Tuco" his name is "Heisenberg." Werner Heisenberg was one of the most important physicists of the 20th century and won the Nobel Prize for developing the theory of quantum mechanics. He is best known for the Heisenberg Uncertainty Principle, which states that one can't precisely know both the exact location and the momentum of a particle at the same time. Heisenberg died of cancer, which is one of the reasons why Walter chose the name.
The poker hand in this episode is a callback to the symbolic advice Hank gave Walt during his intervention; to keep playing even when he's behind, in hopes of a change of luck coming on the river. The river brings a flush card, and Hank folds a hand that only loses to a flush or better, indicating he thinks Walt has taken his advice literally and stuck with a weaker hand that improved at the end. In reality, Walt has decided to make his own luck by bluffing, which alludes to the episode title and his later "bluff" with Tuco.
Just before the end of this episode, when Walter tells Tuco he has to take two pounds in the next order, Tuco answers, "Órale", a Spanish slang word expressing agreement or approval. Close captioning says Tuco's answer is "Oh, really".