I'm hiding behind the parapet... to me Thomas, James, Sebastian, George, Adam, Benjamin are all very similar names. Very nice and inoffensive. Callum (hears rifles being loaded) is a different type of name. Having Callum in with this selection is like calling your children Rebecca, Hannah and Diamanta Bicardi Breezer...
It is a traditional Scottish name, but has been widely adopted and is not in the same 'camp' as the other names on your list. That's why it was surprsising to read it there. Don't mean to be offensive about the name, but it just doesn't fit with your other choices.
I quite like Callum if it is shortened to Cal and you don't live in Scotland.
I must say doubleexpresso I misunderstood your comment about rifles being loaded and Callum. The name also reminds me of the Bernard McLaverty book about Cal the IRA man. But you are not inside my silly head.