Well I didn't read through the 31 pages of posts. I love some of ideas though especially the:
Air Ambulance
Speedometer
Interactive/Destructable Environment
Animals
Out of Town trips
More famous voice acting
Physical appearance damage
What I didn't see and again, maybe I missed them:
The ability to by ammo for a gun you already have.
As far as locales I'd like to see: NY, Boston and Providence and maybe Martha's Vineyard.