I've blogged many, many times about my characters and me fighting about what they want versus what I want.
We've disagreed about names. For example, I had a hero who chose a name I didn't like. I said he needed to pick something else. He said let's just use this one as a placeholder until we find another one. And what happened? The name I didn't like stuck! He out maneuvered me!
And the plot? Forget about it. If I try to write something my characters wouldn't do, they go on strike. I will literally spin my wheels, unable to write a word I can keep until it 1) dawns on me why they're on strike and 2) locate what it was that set them off and 3) rewrite the scene to their liking.
This happened in Eternal Nights. Wyatt and Kendall would not move from the corridor of the pyramid. It usually takes a while before it occurs to me that they're on strike, which in this case led to about six weeks where everything I wrote got cut. Then I figured out that the kiss was the problem, rewrote it so Wyatt was happy, and was able to finish the book.
I had a new situation crop up last fall, though. This has never been a point of conflict before, but luckily it was a minor inconvenience for me and not something I was going to argue about with my heroine. It concerned her vehicle.
As I wrote the scene, I had her parking her SUV next to the hero's vehicle. Only he's driving a SUV, too, and honestly, I couldn't see him in a pickup truck or a car, so it had to be a SUV. Rather than have both characters in the same type of vehicle, I tried to put my heroine in a car. I even researched whether or not she could drive in a VW Beetle comfortably because she's nearly six feet tall. I checked out colors, interiors, features, and was wrote her in the Volkswagen. She rebelled.
No cars. It's a SUV.
In my earlier days as a published author, I might have fought it out with her, but I've gotten wiser with my characters since then. I let them have their way if it's not something important. So I researched SUVs and found one for her that she liked.
Okay, let's be honest. They always get their way sooner or later. I always lose the power struggle. Sadly, my characters are always right, too. That's the toughest thing to take.