I like it. I think it's really cool, but you have to have the right personality to bear it properly I think. I can't imagine it on a straight-laced jock. More of a quirky science geek, or drummer.
My dad works with a man named
Cosmo.
He's an engineer and basketball player. However he gave his kids really ordinary names (
Anne and
John), which might mean that he didn't enjoy being a "
Cosmo" in the US. Also my friend
Mabel's dad wanted her to be
Cosmo if she was a boy. It would have fit her.
For nns I can only think of Coz and
Mo.
Cosmo Julian,
Cosmo Avery and
Cosmo Darcy come to mind.