Attention Automobile Designers:
Carmen A soundproof wall that would come down right behind the drivers seat. They could hear me yell, but I wouldn't be able to hear them!
Mazeway One of those plexiglass shields that limos have between the driver and the passengers. So that I could just make the noise go away.
Jill Miller Zimon Soundproof barrier between my kids and the front passenger and driver seat
Allison One of those separating limo windows between the front seat and the back where all the children, old french fries and farting sound contests are.
cmhl A plexi-glass divider between the front two seats, and the back of the vehicle, totally sound-proof. KIDDING. My real answer would be a high-efficiency expresso machine, since I am always sleep-deprived.

The commercials make it sound fantastic!
Mir OnStar. "Hello, OnStar? I'm hungry, can you bring me a pizza? I'm at the corner of..."
Lin Navigation system for sure and the Onstar ads are really starting to freak me out. Maybe I should get that, too.

Practical
Maryanne I would add a sun roof. I had one once and miss it terribly.
Eulallia Power sliding doors. Ooh, I covet the power sliding doors…
Jelly Heated seats. My heiny gets cold.
Sleepless Mama Dent-resistant panels to the doors.
Lauren That's easy - better gas mileage.
EverydaySuperGoddess OOH! SEAT WARMERS!

Just like Knight Rider!
Summer The capacity to love.
Buffi The ability to speak directly to the individual drivers of other cars. You know, "Hey, BMW lady, get off my ass!" or "Buddy! The speed limit is 60! Why are you going 45?" and my personal favorite "Do not even think of waiting in the middle of the street for your child to come get in this car! We all got the pick-up rules at the beginning of the school year!"

Just like the Batmobile!
ishouldbeworking Auto pilot, or a billing statement with a zero balance
Surcie Remote Control. I have a bad cold, so I’d send the minivan via remote to Starbucks to fetch me a decaf grande skim no-whip Peppermint Mocha.

Just like Miss Daisy!
Jenijen A driver.
Holli Someone else to drive it for me, preferably someone who did massage on the side.

Brought to you by the letter X
Mary For the station changer thingy on my steering wheel to work with my XMRadio receiver. Preferably for it to rotate through my presents. Abuilt in trash can would be cool, too
Mother Goose Mouse XMSR
Barbex Internet!!!! For those inbetween waiting periods where it doesn't make sense to go home but it gets really boring just sitting in the car.