Developer 343 Industries has released an update for Halo 4 that tweaks and rebalances the game's collection of human and alien weaponry.
Available now, the "Weapon Tuning Update," does exactly what its title suggests: It alters the behavior of the guns found in Halo 4. "How?" you might ask. Normally this is where I'd copy/paste a long list of relatively minor tweaks that add up to a slightly different gameplay experience, but with Halo being Halo, Microsoft's fat coffers are still hanging around to ensure that every aspect of the game is well-funded. Thus, at top-right, you'll find a video walking players through the changes found in this patch.
Given how many months its been since Halo 4 first debuted, it may be surprising to some of you to see the game's weapons being rebalanced to this degree, but the goal of the update, according to 343 Industries, is to make the game's online component more balanced, and to "improve the feel of Halo 4 matchmaking." To that end 343 invited a number of Halo 4 community members to their studio to check out the alterations prior to their being introduced to the public. According to said community members, the weapons update is a big improvement.
Whether you believe them or not (or, for that matter, if any of what they've said is true) is currently a point of personal opinion. Realistically we won't know how well this patch fares until its been available to the general population for at least a few weeks. In the meantime, you may as well pick up the patch as it is free and you'll likely need the thing if you hope to play Halo 4 online.