BeReal, a social media platform thats used and only in the phone but theres a python api called befake for it
Newgrounds, a site that is famous among online, as the nature of the site.
IcebergCharts.com, a site focused around creating "iceberg charts", little charts shaped like an iceberg displaying data, may contain user's data or intrests
Geometry Dash, a popular online game that cannot be accessed in the browser.
Fortnite, an extremely popular online game.
The internet archive, an archival site where you can archive data, mirror videos via tubeup, and archive webpages, and they leave a trail in a json file, and tubeup and instaup uploads leave traces behind.
Doxbin, a popular harrasment site that has a comment history and a paste history, may be useful for investigating online harrasment cases
character.ai which is an AI that has almost no filters, and has public osint data unlike ChatGPT