I thought of this while watching a subway $5 commercial. I figured others have some similar ones.
The hot dog/polish sausage and soda special from Costco, Sam's @ $1.50, I do not think you cant find anything cheaper.
Along the lines of hot dogs, the Ikea #2 combo, 2 dogs, soda and bag of chips for $2. Fifty cents extra will get you another hot dog.
A local Mexican rest close to where I work, Mexico 2000, has a chips and salsa special for $1.50
The Vietnamese banh mi sandwich, they are usually under $4 and are very filling.
What are yours?