I just noticed in the halo 4 prologue when Halsey and the.. Other guy... Where talking, Halsey made the assumption that he wanted to replace the master chief and he said the master chief is dead.
So that means they replaced master chief and they didn't know he was alive so when master chief went searching for cortana the other Spartan is hunting him.
No, if they add customizations then higher level people will be more OP than newer people, I know they did this in halo 4 but it was just the weapons not attachments. And besides this is halo not call of duty.
I would have to say the needler because if you put enough into one guy they explode and they lock on, plus in the early years of halo you could duel wield!
I would have t say the energy sword because it is way faster than the gravity hammer
But the gravity hammer is extremely powerful and can destroy vehicles
But I'm going with the energy sword