I am perfectly happy to eat a piece of beast that has been seared to medium over a flame, seasoned with salt, pepper, and maybe some garlic. Just gimme some bread to sop up the juices/blood.
That said, there are many excellent compound butters that go good with steak. I make and serve bearnaise at work; it's the de facto sauce for tenderloins. I can't say that I've actually tried a piece of beast dipped in bearnaise, though.
Sauteed onions and mushrooms, on the side, or on top of the piece of beast, are excellent, especially if there is some thyme mixed into the veggies.
Everyone that admitted to KETCHUP on their steak needs to fork over their Diner's Club International card for their heresy!