This can destroy certain decks that need their mana for other things such as casting creatures, and can force them to budget their mana a lot more than they usually would while you just continue playing (assuming youre playing a deck that is big on mana, that is, otherwise this will greatly affect you too)
While Dobermon's sacrifice gives Takato, Henry, Rika, and Ryo the ability to BioMerge with their partners in the real world, and become Gallantmon, MegaGargomon, Sakuyamon, and Justimon, it doesn't give them any protection against the D-Reaper, and its ability to delete anything it touches
I have loved, since those days, that Magic offers so many different card games that can be played with the same cards
7 Obliterate
In multiplayer, this even has team synergy and great political potential
If a creature with a boast ability is put onto the battlefield attacking, it was never declared as an attacker