Que Bueno
If you like Mexican, Go for "Que Bueno" near Gate B52 on the Denver International Airport "B" Concourse (United Airline's hub). Fast, inexpensive, good size portion, *excellent* burritos. Your choice of fillings, and mild, medium or hot salsa. Very fresh, very tasty, highly recommended breakfast or lunch to grab on your way between flights. You can get them packaged "to go", and the gate agents don't object to your taking them on the flight.

Good enough to make the flight attendants drool, strongly recommended over United's standard breakfast. 9 out of 10, and about $5. Don't forget a couple of napkins though!