If you're trying to remember where you saw this or why it was labeled as "useful," providing a little more —like where you found it or what you were trying to do—would be a huge help.
While that specific text looks like it might be an old username or perhaps a nostalgic reference to early 2000s internet culture, it doesn't immediately link to a specific "useful" tool or well-known service on its own. In many contexts, a string like this might be: sexyangel2007
Sometimes used in coding tutorials or as a sample password (though definitely not a secure one!). If you're trying to remember where you saw
To a piece of media, a character, or a niche online community. sexyangel2007
From the era of AOL Instant Messenger (AIM) or MySpace.