Fatburger has great burgers too. IMO, far better (and more expensive) than In-N-Out Burger.

I might get flamed for this, but in Phoenix Corleones makes the best cheesesteaks outside of Philly. They close early on weeknights, are open very late on Friday and Saturday night, but they're made quickly, piping hot, and always tasty.

O'Brien's is a pretty decent little sandwich shop in Ireland - they even have a few international locations including the Singapore airport. They also have a great chai latte if that's your thing.

I forget the name, but there is a chain mini-grocery + fresh food store in Germany (or at least in Bavaria) that has a daily menu (hot food) plus I think sandwiches. It's certainly a quick and convenient way to get lunch. There's one about three blocks from Marienplatz on Theatinerstrasse very close to Odeonsplatz. I think the name starts with a "V". Maybe "Venzinmurr"?