The fairing bolts weigh only 4g for a set of 5, saving up to 13 grams over a steel bolts. These bolts are sold as fairing bolts for motorcycles, and come in a variety of colors. Normally, bolt tuning is considered being a drastic measure for every last gram. While bicycles do not have fairings, they use several M5 bolts. 4 for the bottle cages, and 1 for the bottom bracket guide. Some people also use them for the front derailer, but these aren’t long enough for a chain catcher. Note that the bolt may have to be cut short to not interfere with the bottom bracket. If you can not cut metal, you can keep the steel bolt, or use an inexpensive even lighter nylon M5 or 8-32 screw, as it requires very little strength. While I doubt anyone cares about saving 10g off of a 500lb motorcycle, these are anodized in various colors and made in aluminum for that reason. These are lighter than the other style of fairing bolt, longer, and have a lower profile head. Their disadvantage is that they use a smaller M3 hex key instead of M4, and tolerances are not as good. At $2 for a set of 6 saving 6.5g per dollar, it represents an exceptional value, very low cost upgrade. It can be purchased on eBay.
Price: $2 [Very Low Cost]
Value: 6.5g/$ ($0.15/g) [Exceptional Value]