A powerful pump spell on the adventure side, plus a good creature to follow up, doing a 1-2 punch with this in the mid-game gets a lot of damage through
Creatures that enter the battlefield attacking will not trigger Master's Guidance's first triggered ability
That said, the sacrifice aspect and the potential for huge mana boosts in Reanimator lists has led to the card seeing steady play in Commander
As if ex's in pocket were not bad enough with only 3 points to take
The enter and attack trigger on Krang & Shredder takes cards from opponents decks, and with a permanent leaving the battlefield under your control (easy), you get to play those cards for free on your end step
Unfortunately, it wasnt properly released through the Japanese Pokemon Players Club in 2005-2006, which is the main reason for its rarity