This newspaper article lists 10 unexpected benefits that some airlines offer even in Coach.
The list includes full cans of soft drinks (something I always ask for and receive), hot chocolate (even on Southwest Airlines), and temporary babysitting.
Also on the list are sanitizing wipes, amenity kits (comb, earplugs, eyeshade, etc.), extra snack packs, bandages and cute wing pins for the kids.
Some people avoid the cost of on-board alcohol purchases by taking their own mini-bottles of booze aboard. The small full bottles are available for about $1.50 at liquor stores in many states, and can be refilled at home.
Of course, you are more likely to receive these if you are polite to the flight crew.