Tenderloin (sometimes called filet mignon) is the king of steaks. It's lean, tender, can add any wanted flavor to it and it will absorb it all, and you can cut it with a butter knife. This is expensive though so only cook this once in a while.
A sentimental favorite. My mother and I made it when I was 7 and it's been a part of our holiday tradition ever since. A fun recipe to make with the kids. A slow cooker will keep it warm while serving.