Instant free bank transfers by IBAN. In comparison with how tightly-guarded personal email addresses are protected (GDPR, etc.), it's shocking how common it is to freely give out your IBAN.
Better than being able to commit ACH fraud merely by virtue of having the bank's routing and account number.
Side note: shout out to both MB Way and Multibanco payments in Portugal that have made it so I haven't have to give payment information to an online vendor in years.