They spend a good chunk of the game catching frogs in Qu's Marsh (there's even a golden frog sidequest), while their main battle ability is actually "Eat" - consuming weakened enemies to learn Blue Magic (enemy skills)
While Counterspell is often printed at uncommon rarity, it did flutter at common rarity in the early days of the game which is the only reason its not higher on this list
If it was discarded to pay a cost, that cost is still paid
Moonshaker Cavalry is a great payoff for having a large battlefield, as it'll give all your creatures a massive stat boost, usually enough to win the game the turn you play it
Loxi: I mention opportunity costs a lot, and utility lands in colorless decks tend to have the lowest of those since they don't really have other lands to lean back on besides Wastes
Introduction of two exciting new mechanics