If you're looking for what appears to be good quality, but cheap as anything, miniature replicas of your favorite Halo weapons, then look no further than Master Replica's models. Pictured is the UNSC BR55 Battle Rifle, made of die-cast metal. The rifle is 3.3" x 6" x 2.8", perfect for a little corner of your desk.
The other weapon model available is the Covenant Carbine, which is a similar size to the rifle. Currently both models are pre-order only, but who isn't used to that from their games retailer by this point? The units will be shipped sometime this fall. You could always place one of these on your Halo Xbox 360, while you wear your Master Chief suit, and drink your Master Chief Mountain Dew. Merchandising, merchandising, where the real money from the game is made. No word yet if they'll add more weapon models, but we're holding out for Needler bookends.