I plan on doing an OOT bag, probably no favors, unless something strikes me as the perfect idea!
As for what to put in there, I've been trying to think of a list so I have some ideas once the time comes - like you said, lotion, bottled water, advil (my guests may need it!), snacks, itinerary, local travel guide, gift certificate to spa/golf/other entertainment, flip flops, t-shirt ...