I have yet to see or hear of a merchant that doesn't require a minimum of at least 1 confirmation. In theory, it might not be needed, at least if there is a sufficient transaction fee to prioritize it.
However, I believe the merchants/processors are all practicing CYA / "better safe than sorry," and requiring a minimum of 1 confirm, for even the smallest transaction, and larger transactions/operaations generally requiring 4 or more confirms.
Are you kidding? For example here in Arnhem, there are plenty of places that accept Bitcoin, and *none* of them requires waiting for any confirmations.
Doesn't matter whether you pay for a cup of coffee, or hundreds of euros for a family dinner in a restaurant. Instant payment, NO confirmations needed whatsoever. That's the ones accepting Bitcoin directly, as well as the ones using a payment provider.
So far, thousands of euros worth of bitcoins has been spent, and exactly ZERO cents have been at risk / charged back / double spent.