I put either salsa on it or Taco sauce.....Any taco or burrito is worthless without a decent sauce. There isn't any kind of sauce you can buy in the store that's good enough, and I've tried just about every one of them.
The best sauces are those bottles of red and green, you get at the taquerias across this country. The red is usually made out of toasted chilies and is always hot. The green is usually made of tomatillos.
Without those, you might as well be chewing on a piece of cardboard.
I used to douse everything with hot sauce but that bugs my stomach a bit too much lately.