The ICQ “uh-oh!” sound is still the iMessage custom sound for my best friend’s contact, because I remember spending sleepless muddy summer nights of 1999 chatting with him on the crazy realtime chat feature.
Yup. It also had random chat feature which i enjoyed quite a lot. Made my first online friends (whom i ended up meeting in real life, and are still friends with to date).
To this day, this 'uh-oh!' sound makes me tingle all over.