My play bike is "The Couch", because some time ago, when he only built hardtail frames, Keith Bontrager had a magazine add that said, "If you want plush, buy a couch."
My old single speed work bike was called "Satan", because it was an evil fucking thing.
I did have a hardtail called Fungus the Bogeyman.
I also have the imaginitively named bikes, The Blur and The Single Speed.
A couple of other bikes are named for their function, The Townie, The Cross bike.