I remember the music/sound when ICQ used to load up. The logo was brilliant. Nostalgia. Circa 1999-2001 when I used it heavily. Best part though: finding strangers and becoming online friends with many of them (without worrying about scams etc).
I don't know if it's nostalgia or silliness, but I've at various times reused the ICQ uh-oh audio as irssi hilight/putty audio bell sound, SMS signal and Discord voice channel join sound over the years. Usually I find it entertaining the first two or three times and then it acts as a very large stressor.
Yeah, the random chats were definitely the highlight. I recall a level of discourse considerably higher than what you commonly find on eg. Omegle now (or 5 years ago or whenever I last used it, anyway).