Here's a few that come to mind

-quad tail lights
-side fender vents
-rear opening hood
-corner mounted windsheild wipers (all years up until C5, they just looked cool when they were on)
-split grille damm*t


I'll reserve judgement on the fixed headlights, but if we've got to have them, I would like to see a quad arrangement like the C2's and C3's had.

Any other ideas?

*edit* rear opening hood, not front opening

 

-Hood needs to open the oposite way (hinged at the front)
-quad tail lights
-side fender vents
-glass hatch (with exceptions for special models)
- Targa roof

 

Quad tail lights.

Concealed headlamps (ya, I know they are gone... they are still on my list of requirements. )

Low / wide stance.

Reverse opening hood.

Split grille (again... gone)

Some sort of side 'gills'.

Crossed flag logo.

Cockpit-style interior.