For aesthetics, GRiD. I've only played the demo, but it's the only game I've ever played where if you hit a wall at even 60-70mph it caves in the whole front end of the car, right up to the bulkhead. Most games will dent the bumper a bit and you just bounce off. Unfortunately it drives like absolute arse.
For sheer *fragility*, as someone said, Richard Burns Rally. Apart from realistic damage, it's just incredibly satisfying to play as you really have to drive the car rather than just guide it as in a lot of rally games. It's the only rally game I;ve played where it feels like the wheels are turning the car, rather than it just rotating about some central point.