Is MM left handed or rights?
Probably ambidextrous
Right handed
right handed
Right handed, I’m sure, because it’s always been portrayed that way.
Are you asking this because Michael holds the hammer in his left hand in the new trailer? Yeah, i saw that too lol
Hammer and knife. James Jude Courtney is probably left handed.
Even then, in the first trailer, Michael spins the knife in his right hand. So I’m assuming he might be ambidextrous.
Thats the doubt…or theres sonething about it…
The 2nd trailer makes him seem left-handed but I doubt Carpenter would change it this long after the original. If anything he’s going to kill with both hands and like others commented be ambidextrous
I doubt the boogeyman is restricted to killing with one hand or the other. Definitely ambidextrous
To me it just seemed weird to see MM holding the hammer and knife in his left hand. He even walked and was looking in the window holding the knife in his left hand. For some reason this really annoyed me lol.
In the original he switches hands while holding the knife but I think we just shouldn’t question the Shape lol! Ambidextrous killer
Those could be because of the shots and/or the angle of the shots. Maybe they could only get certain shots with his body, and the weapon, lighting, etc. if he held it in his left hand. Such as the part when he is holding the hammer, then turns left in the kitchen perusing the robed lady in the new trailer. But then again, what do I know lol. Just notcied the Myers symbol is left handed. 
I just noticed as he is holding the knife walking onto the porch and looking in on the woman on the phone he is holding the knife in his left hand as he walks behind the house, but as soon as he is in the house and walks up behind the woman, the knife is now in his right hand for the kill.
These replies are only assumptions
I’m sure he used both hands.
He’s ambidextrous. Michael tends to prefer using it’s right hand, but he’s definitely shown to be capable with both.
It seems in 1978, he is right-handed. Unless he is using his dominant (right) to do something, such as bust through or open a door. This, at least, is what I have noticed over my years of watching this movie alone. As for the rest of the series, well… not too sure.
Better hope he is right-handed considering the state of his left hand after H40 