The Weaponless Elite (Dual Wielding) Glitch only works on Halo 2.
To see the glitch, go on any level in Halo 2 where you have Elites as allies. All you need to do is get a Needler (this works best, although you can use any weapon that reloads) and fire the weapon until there is no left. Then walk up to your Elite ally. If done right, swap it with him while you are reloading so he has it. He should drop it. When he follows you(or if you kill all allies except him), he will do a humping motion and just walk at an enemy.
An alternative way is to try firing a round while dual-wielding and when you start to reload swap weapons with the Elite.