Jasman Toys

According to a Bungie update posted by lekum, there will be Halo 3 Replicas Guns! They concentrate mostly on realism and they won't be a 1:1 scale, since the guns would be huge because the Master Chief was 7 feet tall and to have a 1:1 scale of the gun he carries would be too large and heavy for the normal-sized adults.

Production Line in 2007
According to Bungie, the plasma rifle will have lights and recoil similar to those in the game. It will also have the real sound effects from the game as well as some of the special features including the “overheating” when shot too many times in a row. The plasma pistol will also have the lights and sounds as well as a recoil vibration when shooting and a “super shot mode” when holding down the trigger that will do more damage.

Where to Buy
"The Covenant Plasma Rifle and Plasma Pistol will be available at your local Hot Topics and other fine retailers starting October 2007." says Joseph Staten, at a Q&A, "The Covenant Energy Sword will be available sometime in 2008."