We've got a few.
There's Katrina, a name someone in here originally felt was her name but has since ceased to be, I'm kinda her but not really. It's the name we use in our day to day since as no one's name it helps us feel the same degree of attachment to it.
There's also the system name, Haven, or more specifically these days, The Haven Coast.
Haven came around when it was just the entity that became my subsystem (Sea) and another member, Cari. We're all big Homestuck fans, Sea was a Rogue of Light (which I later inhereted from her, or perhaps I was influencing that part of her?) and Cari is a Sylph of Void. There's a song on the Homestuck soundtrack titled Voidlight which is a finalized version of a song in the unreleased soundtrack titled Haven and given our aspects we decided to use this as a system name.
We later expanded this to Haven Beach and later Haven Coast when things that'll be covered in the next ask get answered!