Fun. It's not what drives people to leap out of bed in the morning and rush happily to the office, but knowing that work won't be all work certainly doesn't hurt. Fun lifts the spirits, makes onerous tasks easier, and creates an environment in which everyone is willing--even eager--to work hard and well together. As employees and bosses alike put in longer and longer hours, having fun at work is almost a necessity. (I personally try to have as much as possible.)