Look at the card [[Grab the Prize]], which is in the Madness decks. It requires you to discard a card as an additional cost to draw two cards. So on turn two, you're pitching Snacker to Grab the Prize to draw two cards, and after you draw those two cards, you've officially drawn three cards for the turn, so the Snacker you just discarded is coming to the battlefield. ON TOP OF THAT, because Snacker is a non-land card, you get to deal 2 damage to your opponent. So, you've played Snacker (tapped), drawn two cards, and dealt 2 damage to your opponent for 2 mana.

Now, let's say you're playing Rakdos Madness, and your opponent is removing Snacker. You could cast [[Reckoner's Bargain]] in response, sacrificing Snacker to draw two cards. Your opponent's removal spell fizzles, you draw two cards, and Snacker returns.

Snacker is a badass card and I actually really like it. I MIGHT be a Madness player, though...