With Black & White, this changed right away
Its great to do if your opponents attacking creature has lifelink or some other effect that happens when it deals damage to a creature since you can sacrifice your blocker before damage and the effect wont happen
Let's say you cast a Glorious End during your opponent's last turn, if you can untap, play a Gideon of the Trials and make an emblem, you won't lose the game to Glorious End, which means you just Time Walked your opponent for three mana in Standard
This does not necessarily make those decks bad, as their power level can overcome this flaw if the combo it provides is simple enough to win games when it opens optimally
If youre in Australia, for example, you can pick up a Charizard EB World card, as long as youre a member of the EB store program