My wife makes a really good salsa out of mostly fresh ingredients. The tomato sauce is about the only thing that is not fresh. Some of the other ingredients are cilantro, onions, jalapeno peppers, fresh squeezed lime juice, salt and pepper.
Eating it the other day with chips and tacos, I started wondering how it would be as a steak marinade. She bought a couple of (comparatively) cheap chuck steaks for an experiment. I marinated the steaks in her salsa for about six hours, then slapped them on the grill (small Char-Broil charcoal grill). It was a learning experience, but the steaks turned out surprisingly well.
The flavor was quite good, and the steaks were actually tenderized a bit by the acids in the salsa. The only thing I would do differently would be to marinate them overnight, and scrape the salsa off the meat before placing the steaks on the grill. Glops of salsa fell off the steaks and smothered the coals they covered. That made cooking time into a bit of guesswork as the grill was cooled from the smothered coals.
Of course, I'd use a better cut of meat next time. We used the cheaper chuck steak in the experiment, not wanting to risk more expensive cuts in case things didn't turn out well.
I don't know if what we did was in any way unique, but I'd never heard of it being done before, and thought it was worth a try.