No weapon
From Halopedia, the Halo wiki
In forge mode have one person spawn any weapon. Then, have another person pick that weapon up. As soon as they pick up the weapon, the first person has to delete it. The other person should have no weapon. WARNING you can't have a secondary weapon. If you enter a vehicle and get out you will take out your original weapon. If you ever press the Y button you will take out your weapon. Elites have a melee attack when they have no weapon. They will lunge at enemies but are unable to hurt them.
Another, easier way for this is to use the Xbox version of Halo: Combat Evolved.
Go on Co-operative mode on "Pillar of Autumn". On some parts if a player dies, he or she will be respawned back, but without weaponry.
It can also be done in a similar fashion on the Xbox version of Halo 2. It can also be done by charging a plasma pistol and picking up a skull/oddball. If the player backs up as soon as they pick up the skull/oddball, they will have no weapon.
