I am posting here to add a thread for the upcoming 2013 Z. I have categorize the wish list items into minor and major items.
Minor:
Key
flob truck release (handy for opening hatch when both arms are full of stuff)
What is a "flob" BTW?? And you want a GMC when you hit the flip-flop?? 
Sound system delete option (would include the necessary fuse/wiring harness connections)
Put a Black cardboard to cover it.
Combo oil pressure/oil temp gauge
Combo?? 2in1?? Comes with drink too??
Combo water temp/air inlet gauge
Can I super-size it??
A/F gauge for wide band O2 sensors
Improved tire lugs (the current ones are prown to break)
dude, make sure you set the torque-wrench to the correct lbs. 
Center exhaust exit with functional rear diffusor
Single pipe?? WTF....?? 
Engine bay heat extractors (either on hood or on fenders)
Major:
Quaife diff.
Improve throttle response
Step a bit harder on the gas pedal... but make sure keep it legal speed limit, ok?
Improved manual transmission (smoother upshifts)
You know you have to hit the clutch when shifting, right??
Optional tire/rim packages
www.tirerack.com 
Increase low end torque and elinimate the throttle response between 2k-3k rpm
do you mean max torque at 1900rpm and redline at 1999rpm?