The Shotgun in Halo 3 is hands-down the worst version of the Shotgun we’ve ever had in terms of gameplay, given it’s small magazine and the fact that it is only a 1-hit kill at point-blank range.
But the version in Halo 3: ODST is even worse because of the 50% bullet damage penalty versus energy shields, which makes it a two-shot kill against fully shielded Brutes… and it only has 6 rounds in the magazine! It’s especially useless in Firefight due to extremely limited ammo reserves and Brutes spawning in large numbers.
The solution? Convert it into the Halo 2 version. Give it 12 rounds in the tube, a longer 1-shot kill range, and remove the 50% bullet damage penalty versus shields. Seeing as the game is set during the events of Halo 2, it would also be thematically appropriate.
It would be very easy for 343 to do; they could just slip it in with the next major update, and it would not hurt the balance of the game at all since Halo 3: ODST doesn’t have PvP.