Maybe because it doesn't go with your surname, you know someone with that name, it's just a bit too "out there"...
Alex has always been my favourite, favourite name for a boy - but since it's DH's name, that's ruled out for me. At least he has it instead!
There are also a lot of girls' names that I like, but don't know if I would have the balls to use - my family all have very traditional, ordinary names. I like Marina, Beatrice, Emilia...
How about you?