Well, I live in Las Vegas NV, the city that reinvents itself continually. There aren't many "old time" Mom and Pop places, so I'll suggest goodies at the various casinos.
Not too surprisingly, the smaller casinos have the most interesting food.
Breakfast: The Golden Gate at 1 Fremont Street--the oldest casino in Las Vegas. Very good breakfasts at the Bay City Diner, and (as a midmorning snack) the famous 66 cent Shrimp Cocktail (popcorn shrimp, but still good) at the San Francisco Shrimp Bar and Deli (which also has good sandwiches).
Snack: $1 Vienna Beef hot dogs at the sports book in the Barbary Coast at the Strip and Flamingo, or at the Suncoast on Rampart a few blocks south of the Summerlin Parkway.
Lunch: Our favorite (yeah, it's not road food, but the place is family owned, homey, and close to home) is the sushi special at the Narita Japanese Restaurant, on Tenaya just north of Cheyenne.
First, we're talking buffets here.
Best inexpensive buffet is the Garden Court Buffet in Main Street Station (on Main Street just north of Fremont). Food is simple, but the variety is great Cost is $10.29 to $14.99 depending on the night of the week.
Best Expensive buffet is the Aladdin Spice Market Buffet at $19.99, but worth every penny. Delicious food, including Middle Eastern/Greek food, seafood, Italian food that isn't just spaghetti and pizza, and superb desserts.
Best Coffee Shop Special: Lucky's 24/7 at the Hard Rock Hotel, Paradise and Russell. From 4 PM to 7 PM (but it's not on the menu--just ask the waiter/waitress) they have three Twilight Special dinners for $5.99: prime rib (my favorite!!), a half chicken, or bowtie pasta primavera. The rib and chicken come with potato or vegetable. All three meals come with a nice salad.
Best Bar Food: Triple 7 Brewpub at Main Street Station. Try the pizza or the ribs, as well as the microbrews.
Coffee Shop I've heard about but haven't been to yet: the Peppermill, near the Riviera on the Strip. The place looks like a coffee shop right out of the 60s, and the food is supposedly excellent and generous.