The new Halo 4 Weapon Sounds trailer offers plenty to see and hear. For the most part, everything on-screen is explained to some extent to provide viewers with what they're seeing.
At one small point in the trailer, there's a split second in which you can see what appears to be the Promethean Pistol—a weapon which has yet to be officially announced on the Halo Waypoint or any other official source.
In Halo 4, you can pick through several different secondary weapons in addition to your primary weapon in your loadout. Thus far, we've only been privy to the human pistol and the plasma pistol. When switching to a sidearm, players can throw grenades a little faster. Switching from primary to secondary weapons is something you can pull off more or less instantly, giving players a good chance to use it as a backup weapon in case they run out of ammo or need to switch to something up close and personal.
The video offers a glimpse—a first look–at what fans think is the Promethean Pistol.
It should be noted that the Promethean Pistol isn't a flame-based weapon as some have speculated. The explosions you see in the trailer are the result of an exploding rocket fired by a rocket launcher, and not the sidearm.