Brakes
Sometimes small things can make a big difference. In this case, switching from a Gyro setup to a regular cable can save slightly over half a pound. And to all you bar spinners out there don't be deterred; up to two full rotation can still be pulled from a properly lengthened brake cable.
Bars
Profitable results may vary depending on your current bar selection, but shedding your four piece handle bar in favor of a two piece jumping bar can again save you upward of half a pound in you front end.
Wheels
In the past five years, 48-spoked wheels have become the normal at the tails, the switch from your current 48s to a well-built set of 36-spoked can save you a hopping two pounds.
Cranks
A lot of new jumping bikes on the market are coming stock with forged three-piece cranks, which are welcome alternative to the not so quite as strong one-piece option, but they do have there weight oriented drawbacks.
Chain Wheel
So if your bike doesn't double as a nighttime street machine, and you choose to favor a standard chain you should consider a standard width chain wheel. you'll loose half the current chain wheels weight and gain a smoother running drive train.