Here's some big city places that order food:
Strip Clubs: Er, um, gentlemen's clubs. Usually a great tip. You may have to wait a few minutes if the customer has a customer of her own. Sometimes the doorman might cover the bill for her, and that's a good way of getting screwed out of most of your tip.
The girls are usually very appreciative, and tip well. They are members of the service industry and often abide by the code, which means that you tip extra coz assholes don't.
Not always the run come true, some of the nastier places the girls just "aren't making any money tonight" and stiff you, thinking that the sights are tip enough for you. Generally when that's their attitude, there's an obvious reason that they're not making bank.
I have actually delivered vodka to a stripper at work. She requested that I take great pains to hide it from the bartender. Yikes.
Generally, a preferred run.
Hotels: Again, the nicer the place, the nicer the tip. People may be sleeping, showering, smoking pot, entertaining hookers and tips are almost always mid-range and up, coz people who don't have money don't stay in hotels. If of course you get college students, well, they save up all year so that they can buy beer and bunk weed.
What people staying in hotels don't realize is the extra effort that runners take to get the order to them. Yes, the elevator ride (or stairs!) and long hallways cost us time. If you can run 8 deliveries per hour under normal conditions, four hotels would be a stretch.
Can be worthwhile, but don't miss a confirmed good run over it.
Office buildings: These are tricky situations. Not only do you have to do the elevator/hallway thing, as in a hotel, but your timing is crucial. Lots of people need to be fed during the lunch hour, and tempers can flare from the people on the low end of the corporate hierarchy.
I've delivered to people on the verge of losing it from a 2-hour deviation from their regular feeding schedule. These customers are either completely appreciative of your existence or maniacally greedy.
Of course, you can also get the occasional platinum card run. These are usually good, especially if it's a corporate lunch.
(somewhat) OT: Now that I work in an office, I generally wind up tipping the driver even if I'm not getting food. I may want to someday. I've instructed my cow orkers on the what to do, but I'm having a hard time getting them past the "kill the courier, the food is wrong" impulse.