First, skip to 8:06 to get to the glorious moment of unabashed joy:

The card he's discovered is the Black Lotus (Alpha), an incredibly rare card valued at about $27,000 (as of November 2013) and part of the legendary Power Nine set - a select group of cards printed in 1993/1994 that were unusually powerful (and now banned from most competitive play). It's text reads:

Adds 3 mana of any single color of your choice to your mana pool, then is discarded. Tapping this artifact can be played as an interrupt.

Since it costs zero energy, it's incredibly useful and can change the balance of power in a game very quickly. Pro player and writer Zvi Mowshowitz has gone on record saying it's the best card in the entire game. And now openboosters has one of his own, as well as the sense of pure happiness that comes along with it.