Amorphophallus titanum, usually called the titan arum but also also known colloquially as the "corpse flower," is the largest known unbranched inflorescence in the plant kingdom. That means that there is a larger flower—one—but it is actually a cluster of flowers, far less impressive. The flower, whose official name comes from the ancient Greek for "giant misshapen phallus," earned its corpse connotations from the smell of its bloom, which is often compared to a rotting carcass. In other words, it's got a lot going for it.
The United States Botanic Garden happened to have one of these beauties on view in preparation of it's death-stench bloom. I arrived to early to see that, but caught it just beforehand. It is a sight to behold, and re-instills a proper fear of plants that is often lacking in modern life.
There is, however, a very cool time-lapse video of this particular plant blooming: