With its dark fantasy artwork and eerie presence, Nightmare quickly became an iconic card, often appearing in core sets for years after its initial release
You can also destroy a dork and lose two life
Overgrown Battlement is a real workhorse for defender decks, taps for absurd amounts of mana once you've got your walls in place, and can produce infinite combos with the right combination of untap effects
The more combat orientated and aggressive you are the better this is in the build at least
Then you can also return two to the battlefield from your graveyard, and as you are churning through your deck discarding them, drawing two cards a pop, you'll easily have enough few to toss two onto the battlefield for free
I think the Bob's Burger one is particularly good - I love a drop that's focused specifically around one MTG commander - but then there's the usual overpriced lands, and lairs lacking value