This is a redstone banking machine that I made a while ago. Unlike other ATMs, this ATM includes an extra security feature, requiring users to submit two items to access their account: a user ID and their own secret passkey item, mimicking the username and password situation on most websites.
Simple UI: Just a minecart, a button, and a dropper.
Light indication system: Shows users whether their transactions are accepted or not.
Security: Providing an incorrect passkey will cause their transaction to be declined. This includes trying to use a different account's passkey; the user ID and passkey must be tied to the same account.
Flexibility: The most advanced feature of this machine is the ability for it to automatically change a user's passkey without the user going behind the scenes. It all happens from the UI in the front.
This Minecraft map works best in 1.16.x. Download it from MediaFire, and be sure to only move the Map folder into your world saves, not the documentation.