My mother is a wonderful cook, but my father and I have been in competition for the last 25 years or so to see who the better cook is. Finally, I think I have him beat!
The first dish I mastered would have to be grilled cheese and tomato soup. My friends and I would always sneak away from school when we were in high school and go to my house to eat lunch. I would always find ways to kick up canned soup to make it interesting. My mom would be upset when she got home to see half the food in the house gone, "Again." The first with any technical difficulty would be eggs benedict.
My favorite thing to cook by far is a Sunday tradition in my house, French toast. That is my wife's and daughter's favorite breakfast, and my daughter and I get up early on Sunday, go shopping and make French toast together. Wouldn't trade that for anything.
I really learned that you have to be extreamly versatile and open-minded. Be ready for anything and react. Trust your palate. More importantly, you must know who you're cooking for and adjust to please them, whether a hungry Marine or a Michelin-starred chef.