As an electronics experimenter I would have to say the REAL eternal chip is the 555 introduced in 1972. It's become a bit of a meme: You could have used a 555 for that!
Unfortunately, those days seem to be gone. Now any time I see someone point out "you could just use a 555 for that", people are replying "I just threw an PIC/AVR/STM32/RPi in there instead...software is so much better than having to do math to calculate those R and C values".
They were always more flexible, are usually more accurate, and are often easier to engineer. With the price point now being roughly the same, it makes zero business sense to go for a 555.
"You could've used a 555" is becoming the new "you could've used a punch card"/"you could've used a vacuum tube": true, but would that make it better?
One of the more famous toys using it (in blob form) is the Executor/Echo Keyller keychain: https://youtu.be/20W6AJuMjEk