For the record I prefer to teach, guide, and counsel rather than dispense punishment. I do time outs when specific requests are ignored after a few warnings, or for hitting.
An example of my daughter's behavior just happened. Friends are over and everyone is running in the backyard. We have a ton of clover in bloom and the bees are all over the lawn. My son has been stung twice today, but since he has no adverse reaction to stings (beyond initial pain and the tiniest of localized swelling) I keep reminding him to wear his shoes and inform him of his choices and then let him make is choice. He is also 5.5 years old. I've also been stung today.
My daughter, on the other hand, had her first two weeks ago and it was scary. She was stung on her toe and her whole foot swelled up with blisters. She ran a fever for two days and had intense pain for the first two hours, and distracting pain for the next two days. I go outside with a pair of rain boots for her to protect her feet from bees. I ask her to come to me so I can put boots on so she doesn't get stung. She starts coming for me and then runs away so I have to chase her down, yelling at her to stop running so she doesn't step on a bee in her frantic escape from me.
I finally catch up with her and put her boots on to have her kick them right off. I give her a choice to keep her boots on or come into the house. She yells "NO!" about both options but puts her boots on. I watch her for a bit while she sees how far she can slide her boots off before I take her inside. Eventually she keeps her boots on, but sits outside and cries about having to wear boots outside.
If I had to take her inside what would typically happen is she would try to run outside, so I would tell her, "Stay inside or sit in a time out." If I would have to up to a time out she would probably not stay in it, seeing how far she could slip off the chair before I would come back to her and "fix" it.
I know it's a battle of the wills, I totally understand this is normal 3 year old behavior. But I don't feel like I have any ante to up. I feel like her need to defy me is more important to her than any punishment I can give her. And there are times she needs to listen to me, so she doesn't get stung, or she stays out of the street, or she doesn't get hit by a car, or whatever. Sometimes she needs to listen and she just won't.
And because when she goes through these phases I only discipline (punish) on what really matters it makes every choice she makes pretty important as far as safety goes.