Rear speakers, a clock thats visible, an oil pressure gauge, a temperature gauge, a voltmeter.

 

CAD plated rotors.
Better stereo (rear speakers).
Removable *#!@$ sunvisor airbag stickers!
Key with the automatic lock/entry functions built in the key head.
Top that automatically folds into a hard shell tonneau cover.

 

Better stereo (at least the head unit)
From the moment I sat in the car I did not like the feel or shape of the shift knob. I have made my own now and it is much better and usable from any angle. I also raised the front of the seat 1/2 inch and now have decent thigh support. Very subtle, but it annoyed my 30" inseam legs. Feels great now.

 

Here you go.

http://www.ricks2k.com/products/reargears.php

 

I agree with strike's ideas but these are the definites imo.

A high performance car really needs this kind of accurate monitoring and making it standard would reduce the cost as opposed to installing aftermarket items. Would also make it better aesthetically probably since the entire desing would be amalgamated.

 

Highly agreed!

 

The most useful mod I've done was Muz's convex drivers side mirror. It has saved my butt on a few occasions when I've had to drive top up.

Less useful however I like them:

Upgraded stereo
18" Wheels