Back in the late 90s, ICQ's "oh! oh!" (incoming message) has been used in media items (such as TV) about online threats such as malware, phishing, or just anything concerning children (such as online predators). One cool thing though was that there were entire sound packs to turn your ICQ into something else. And if you'd use it as ring-tone on your GSM (before that smartphone age) people around you would recognize it.

I guess I could still use it when my wife messages me on Signal.