Brakes:
Do you really NEED a front brake? Rip that crap off for some considerable weight loss. Come to think of it, do you really NEED brakes at all? I ride brakeless and I do just fine. Also, is that fancy gyro REALLY needed? Of course not!

Handlebars:
Get a 2-pc bar, it's much lighter than a 4-pc. While your at it, trim it down a bit for some extra weight loss.

Rims:
Most everyone has 48-spoked wheels nowadays. Getting a good pair of high-quality 36-spoked wheels can save you up to 2 Lbs. depending on the thickness.

Tires:
A good pair of dirt tires can be up to a pound lighter than some of the super-tough street tires on the market right now. I use Maxxis Ringworm tires that are fairly heavy but they're rating for 110 PSI. Try to stay away from 100+ psi tires.

Cranks:
Forged 3-pc are unnecessary. I use high-quality one-pieces since I've learned to land good and lightly. If you MUST have 3-pc cranks, get some good 3-pc tubular cranks.
Chain:
If you're thinking about getting a heavy burly thick chain, consider keeping the standard stock chain. Get a long-lasting high-quality chain.

Sprocket:
Use a stock sprock. Stay away from sprocket stalls/grinds and yours should last.

Seat Stem:
My seat stays pretty low and so I've cut off the unnecessary length. Be careful and don't go overboard or your family jewels may pay when your seat stem falls off just before landing that no-footed x-up...

By Rider Gonzalas