[Word?]

So yea,

I've been weight lifting more now, than I ever have. And I was thinking, what muscle groups should I be training harder, so I can make snap shooting easier?

Off the bat, I'm thinking

Core
Back
Shoulders

What else?

[TheGraveDigger]

Calves
Quads
Lower Back
Triceps

I always get on the treadmill for a good 30 minutes to an hour for a good two weeks before game time to prevent myself from draining.

[The Inflicted]

I would think snap shooting is more about muscle memory than strength training.
The only way to get better at it is to do it, preferably with paint, a target, and some sort of cover to roll out from.

[VESIUS]

Anything to do with your legs.

[Nikilwig]

Train everything. Make sure you're balanced on your legs, most people are too quad and lower back dominant, make sure you put a lot of focus on your hamstrings and glutes. Doing rows for upper/midback will. Any form of squat will help especially if it's encouraging thoracic extension to stay upright. Deadlifts are good.

I don't see why you should neglect any muscle groups or focus on just a few. You're workouts should include all muscles. No sense in not training everything.

[Word?]

That's true about the muscle memory thing, the best QB's in the NFL don't have tree trunks for arms. But they don't have twigs either. I think there's a medium to be at for effective improvements, and that's what I'm trying to focus on.

But nikilwig, I do already train everything. But like Ahhnold was saying in pumping iron, his weakness was his legs, so he trained them extra hard. On top of an already existing full body workout.