You are in good company! A 2yo who doesn't say no and dig in his/her heels a thousand times a day is not developing normally – OR has a parent who knows how to recognize the child's natural needs, and empathize just enough to swing the child around 180 degrees.
All behavior is a means to get some need met (pay attention to your own behavior/reactions/tone of voice for a few hours, and you can see the truth in this!). Especially in such a young child, behavior is pretty spontaneous and based on underlying needs – your son is beginning to recognize himself as a separate person with his own set of desires, and he longs to assert control that allows him to explore this separateness. (Kids who don't/can't go through this stage often have some developmental delay.)
It's so important not to take a child's behavior personally. He's really not rejecting you or your values, but he's expressing his own perceived needs in the only way he has. It looks and feels like stubbornness, maybe even meanness, because a 2 year-old's emotional repertoire and vocabulary are so limited. In truth, without your limits and requirements, he'd feel confused and lost. But he wouldn't know how or why.
Instead of more intensive pushing or pressuring from adults, kids generally respond positively and quickly to "I see by X behavior, you want/need more of Y. I really, really understand. I wish we could give you as much Y as you want. More, even! Now, let's go and do Z, so you'll have some time to do Y afterward."
My grandson never has reason to tantrum, and his acting out has almost disappeared since instituting this approach a couple of years ago (he's now 4.5). Though he does receive the logical consequences for his choices, punishment as a parent-imposed ritual has virtually disappeared from his life – there's no need for it. His parents (and other nurturers) don't have to coerce or manipulate him, or seldom even raise our voices, to get his calm, respectful,or often even cheerful, cooperation. He knows we're on his team, and so he's happy to be on ours.
If this sounds as wonderful to you as it is, teach yourself why children become balky and stubborn at two, and how to respond, and you can melt away a tremendous amount of that youthful resistance. Three fabulous resources for helping you in this follow:
The Happiest Toddler on the Block by Dr. Harvey Karp (you can also google this for some great little videos showing him putting his techniques into action);
Also the book Raising an Emotionally Intelligent Child by John Gottman, and the concept of Emotion Coaching, another term you can google for lots of useful information. (Here's one good link to get you started: http://www.education.com/reference/article/important-pare... .)
There are also some terrific books working with related techniques. One of my favorites is by Faber and Mazlish, How to Talk So Kids Will Listen, and Listen So Kids Will Talk. The methods make for good emotional connections, resulting in happy, cooperative and (mostly) obedient children.