Halo: Reach was fun to play, but I couldn't help be annoyed at the many overpowered weapons. Halo 3 had way more balance between most of hte weapons, and it had way less power weapons. Even the ones that were power weapons weren't as overpowered as the ones in reach (The only change I like is the Rocket Launcher). I'm hoping that in Halo 4, this changes. Hopefully almost every weapon there has its own advantages and disadvantages that differ from one another (though there are exceptions, I don't want a weak rocket launcher). Like the SAW, hopefully it has a lot of recoil, but deals more damage, rather than just being a better version of the assault rifle. This way, a player wouldn't always choose one weapon over another. They would have to practice with each weapon and see which one fits them best. I think this would increase the strategy and overall fun of the game.
I also hope automatic weapons can get headshots (or do about double damage when aiming at the head). This way those MLG players will stop insulting me whenever I use an assault rifle.