Serenity?
I think it's pretty. It's my favorite word as well . The only issue is, while I think of it as being a virtue name like Faith, Constance, etc, it comes off more as one of those names like Destiny or something, doesn't it? Pity.
BTW I wouldn't use this for a first name, I'm trying to convince DH it'd be a lovely middle name for our someday daughter.