Breya is pretty straightforward good stuff and mana, with a commander that Shriekmaws their commander and lets you cash in extra mana rocks for the same thing later
Others, like Inkmoth Nexus or High Market, only produce colorless mana
Whispers of the Muse (T1, Ext, S, Block) A favorite in "Turbo Xerox" (a blue deck which used minimal land but a ton of cantrips to thin out the deck), Counter-Phoenix (Shard Phoenix + Forbid) and Tradewind-Awakening (put Awakening on the stack, tap all your lands for mana, untap all your lands), Whispers has what might seem like a hefty price to pay for one card but you get to do it turn after turn after turn
Nadu was a legendary design mistake, and one that very few players are sad to see gone
While Magic: The Gatherings standard deck construction rules typically limit a deck to four copies of any one card with the same name, the Nazgl cards feature a written exception in their rules text allowing all nine to be included in the same deck