Non-wasting Ammo

On halo 2. If you come across a group of enimies, if the appropriate weapon is low on ammo (ie. 1 bullet), you can give it to your allies. They would use and use, and if you trade back, you would have the same ammount of ammo as what you started with. This is a good trick when comming across large groups of enimies. But be warned, It's best if you protect your allie, if you don't, you may have to use it.