You may cast it without paying its mana cost if its a spell with lesser mana value
You definitely need to have a lowish curve to take advantage of this, because you need to hit two creatures when you cast it for it to be worth it -- but I think that'll be the case for most decks
Similarly, of the hundreds of cards that Mark Tedin illustrated (including ones paramount to the narrative lore of the game), its the Chaos Orb that was his choice for the banner of his website
The best creature type is hard to define, but some metrics can be used to narrow it down: If youre looking for creature types that make good creature-focused (i.e., typal) decks then you probably want goblins, humans, or elves
Of course, no army is complete without a competent general, so lets look at the best token commanders in Magic
Then the splashable one will also gain you 7 life in case you tap out to save you