Halo 3 or Reach, I don't see how Halo 4 can be of any help since Theater only works for matchmaking. Halo 3 is good since it has a variety of maps and it also has some really cool elite animations if you can get them without weapons. Reach is nice since it has forge world, and the graphics are a bit better looking. If you are looking for covenant battles in your machinima I'd also suggest reach since it has customizable firefight.