I don’t think roughhousing leads to whining. If he gets that impassioned over the video games, however, I think you need to tell him that he loses the privilege to play when he’s abusive with the toys. Give him ONE warning (I think it’s reasonable to say, when you threw the controller yesterday, that wasn’t an appropriate response to losing the game. It’s okay to be upset, but it’s never okay through throw things. If you throw the controller again, you will lose the privilege to play the game.) If you’re playing together and you’re right there with him, take the controller from his hands if he looks like he’s about to toss it and put the game in an unreachable place for at least a day.

If he’s throwing a fit because his sister is eating berries, tell him that no one gets anything in your house by whining or crying, but if he wants to ask for some berries he can say, "mom, may I have some berries too, please." If he can’t say it after you model it, DO NOT give him berries. He’s three, he’s capable of mimicking you even if he’s not coming up with it on his own. If he keeps crying, get down on his level, look him in the eye, tell him that you’re sorry he’s frustrated, when you don’t get your way you get frustrated too… would he like you to hold him while he’s upset or would he prefer to be alone. If he continues crying for berries, tell him you’d like to give him berries when he asks for them appropriately, without whining or crying.. but if he needs to cry, you’re happy to hold him until he pulls it together. If he says he wants to cry, tell him to let you know when he’s done and ready to talk. (My daughter will literally cry for 15 seconds and say, "okay, I’m done crying now.")

When he whines, say "I don’t understand that noise. You want something, talk like a big boy". Then turn your back and walk away.

When he wants something his sister has, say "If you want berries ask me politely. Talk like a big boy".

Before you allow him to play games, sit him down and tell him that if he throws the controler, screams or whines, game time is over. If he can’t play properly, he won’t play at all.

FOLLOW THROUGH.

The second he whines or throws it, take it. Put him in his room. Tell him he can have another chance later (an hour, the next day – whatever you think is right)

The second he talks properly, bend down, smile into his eyes and tell him how much you like it when he talks like a big boy.

HINT:
This is new to him, so he many not know exactly what to say.

If he doesn’t immediately respond with "big boy talk"…TELL HIM what to say.
Example: The berries.
Say: "If you want berries, ask me politely".
Wait a second – if he doesn’t respond
Say: "Mommy, please may I have some berries".
Make him repeat the words – then give him berries.