I'm not really a food-driven person but even I have to admit that one of the best benefits that Google provides is its free food.
Not only is the food free, but there is variety of food, the quality of the food is excellent, the attention to detail in describing ingredients is thoughtful (posted right by where the food is being served so if you have an allergy to something specific you can avoid that food), and there are over 22 places on campus to try out different types of food.
You can eat Mexican, Chinese, Japanese, Indian, Californian, Mediterranean, or Italian cuisine at one of the many cafes on campus in Mountain View.
You could say I am not a box lunch person. And at Google I don't have to be. I really don't like "fast" food like sandwiches and while I enjoy salad, I can't have "just" salad for lunch because it's cold and doesn't feel sufficient.
Google provides a hot breakfast and home-cooked lunch to us and it's healthy and tastes great. I've got to confess that this benefit alone made me feel happy, secure and loved (yes, loved! It surprised me how I responded to this at a very visceral level, seriously) which in turn made/makes me satisfied, productive and focused.
The best part is that you don't have to eat the same kind of food every day. With so many cafes, you can choose a variety of places and types of food to eat. This makes you vary your routine, and discover new places and encounter new people. This in turn makes work life feel less predictable - that's important for me because I get restless with routine - and I can eat at a new place and get back within the hour.
Also there are always microkitchens in every building, where in between breakfast and lunch you can make a snack, have a cappucino, eat fruit, indulge in chocolate, or hydrate with bottled water. You might think Googlers eat all the time - actually we don't, but to know we could eat at any time if we needed to - like if we had a meeting and missed lunch somehow - is reassuring.
I hope Google never takes away the food benefit since it provides such good will to its employees, and distinguishes Google in an important way from many other companies.