There are some secular (Amy Grant's secular music for example - I realize she's a christian artist too) that I WOULD listen to in a car with Christ.... 50 cent is not one of them

*not my style anyway*
Songs about relationship, and heartbreak and happiness, and success, should be fine (barring objectionable content like sex, drugs, etc). Example (as I think of them...) Martina McBride - Happy Girl... what's wrong with this one? (Lyrics: I used to live in a darkened room
Had a face of stone
And a heart of gloom
Lost my hope, I was so far gone
Cryin all my tears
With the curtains drawn
I didn't know until my soul broke free
I've got these angels watching over me, yeah
Oh watch me go
I'm a happy girl
Everybody knows
That the sweetest thing that you'll ever see
In the whole wide world
Is a happy girl
I used to hide in a party crowd
Bottled up inside
Feeling so left out
Standing in a corner wearing concrete shoes
With my frozen smile
And my lighted fuse
Now everytime i start to feel like that
I roll my heart out like a welcome mat
Oh watch me go
I'm a happy girl
Everybody knows
That the sweetest thing that you'll ever see
In the whole wide world
Is a happy girl
Laugh when i feel like it
Cry when i feel like it
That's just how my life is
That's how it goes
Oh watch me go
I'm a happy girl
And i've come to know
That the world won't change
Just 'cause I complain
Let the axis twirl
I'm a happy girl
Oh watch me go
I'm a happy girl
Everybody knows
That the sweetest thing that you'll ever see
In the whole wide world
Is a happy girl
Oh,yeah oh,yeah
I'm a happy girl)
I realize it talks about being at parties, etc... but it's nothing objectionable. Anyway, that's my 2 cents.