There's a chance Bitcoin will hit growing pushback over its energy use, and maybe even a new primary coin emerge at some point. Most people here probably figure NANO could take on that challenge.
What other coins are out there that NANO is competing with?
Is NANO the only feeless coin? The lowest energy usage coin per transaction?
Is there a coin that offers most of what NANO does but without a public ledger?
edit: just to clarify, I see nano as being a potential everyday currency. Buy a coffee, pay rent, split a dinner bill, sell something on gumtree etc. It has a great combination of traits for this use. I'm looking for other coins/projects that offer similar. Thanks already for the great suggestions below too.