Also being able to kill X/4 creatures for red decks is huge: cards like Primeval Titan, Tarmogoyf, Deaths Shadow and many more were a nightmare for red based decks, but now you have a very good and versatile tool in Unholy Heat
But the core idea of using creature cards as removal has only become stronger over time and in decks which are built around the assassin type, there are ways to make murder even more rewarding
Losing a creature a turn is a hard pill for an opponent to swallow, especially once it costs you no investment past the initial one mana and one card
#12 Goblins are awesome for tribal for some simple reasons: 1) A lot of them are already awesome and diverse in their awesomeness
1) Being paid to play Magic Top Ten List #1 - Top Ten Odd Questions I Had To Answer in the Unhinged FAQ 10) What counts as an insult
You cant discard cards straight from your library, battlefield, or exile