Great benefits package. Cold, late nights.
Great company culture. Provide room for employees to think independently and bring out the best.
I was just an intern, but I know that the benefits are quite good. For instance, they will pay for furthering your schooling, although I admittedly can't remember what percent or how many courses per semester or year.
Good health insurance benefits as far as coverage and out of pocket costs. Offer health, dental, vision and flex spending.
List based on reports from current and former employees. It may not be complete.