Anything that is not directly related to your work. For example, who cares if you get free soft drinks or not? What really matters is what the work is like.
Perks don't make a soul-stealing job less soul-stealing...but if I have a choice between gourmet food three meals a day (Google) and a coffee maker that no one ever cleans (several companies I've consulted for--at $125/hour) I'm picking the gourmet food every time.
It shows a lack of respect for your employees to treat them poorly. It also shows a lack of foresight to not realize that if you don't feed your people, they will go out to lunch most days. Have you ever been out to lunch with people who don't LOVE their job? It's an hour, with drinks, much loudness, etc. and they all come back a bit dazed and don't get anything done for the rest of the day.
Anyway, free snacks and drinks (healthy ones please) is the minimum I'd tolerate. I'm cantankerous, of course, and don't play well with others--I've worked for myself starting businesses since I was about 22 and don't have any plans to ever work for anyone else (except in the event of a nice acquisition, but even that isn't high on my list of desires), but I think a lot of nerds feel the same way. We can make good money doing all sorts of things, including working from home in our underpants, why would we put up with a work environment that is any less enjoyable?
