If there was an award for shear rule ignorance this post may win it, but here I go...
If you Brain Freeze for more cards than in your opponents deck do you win on the spot or do they have to "draw" a card to actually lose?
Always good to quote the rules, so here is the the significant section
102.3. There are several ways to lose the game.
102.3a A player can concede the game at any time. A player who concedes leaves the game immediately. He or she loses the game.
102.3b If a player's life total is 0 or less, he or she loses the game the next time a player would receive priority. (This is a state-based effect. See rule 420.)
102.3c When a player is required to draw more cards than are left in his or her library, he or she draws the remaining cards, and then loses the game the next time a player would receive priority. (This is a state-based effect. See rule 420.)
102.3d If a player has ten or more poison counters, he or she loses the game the next time a player would receive priority. (This is a state-based effect. See rule 420.)
Bolding mine. So technically, once someone gains priority after someone has tried to draw from an empty library, they lose.
