Now, onto the bad: the price
These range from mildly effective to full-out wild, such as the pegasus rider Archon of Suns Grace, who can create 2/2 flying pegasus creature tokens everytime an enchantment enters the battlefield under your control
Foil $75 equal to the sacrificed creature's mana value.
The big downside with Grim Giganotosaurus is that it doesnt have a built-in trample effect, making it susceptible to being blocked by little 1/1s all day long
Transform sideboards can be fun and impressive when they work out, but I recommend turning to it only as a Hail Mary, when nothing else is working
Dismember also works well because, even though you lose 4 life to cast it, you recover half of that because its mana value in MTG is 3