Lightweight wheels and tires are nice, but seriously "best bang for the buck" weight reduction? What are you smoking? How much did you pay for all 4 wheels and tires?
Best bang for the buck is removing uneccesary **** from the trunk etc. That's FREE.
After that pretty sure best bang for buck is a lightweight battery. Then maybe flywheel(~16lbs less rotational mass), lightweight underdrive pulleys(not much static weight saving, but losing rotational mass is nice).
Keep in mind the flywheel will make the car a bit less streetable, more difficult to smoothly go from a stop. Depends how tolerant you are of things like that.
If you get other power adding mods, keep in mind that some of these options often can save a bit of weight too, win/win situation.
Deleting cats by switching to longtubes or test pipes saves quite a bit of weight. I just got my longtubes installed, and when I get around to getting a catback, I plan on probably getting a single exit exhaust, to save a few extra pounds.
All the CF hoods I have seen actually WEIGH MORE THAN STOCK. Don't get that garbage with weight reduction in mind.
Anyways there's a whole weight reduction thread over
here