I don't have three, but I have two.
1) Providing health insurance
Providing health insurance that the company can afford to offer, especially if the company is small, is a challenge. Some companies split some portion of the cost with the employees, which helps, but it is still cost-prohibitive for the employee to take advantage of it. Thus, they don't really have a health insurance benefit.
2) Providing employee retention benefits
The cost of replacing an employee is very expensive. Benefit managers struggle with what is a good incentive to keep current employees. I've seen some companies offer expensive watches, autos, etc., at a certain anniversary date with the company.
3) Sick pay policies
Someone recently posted they were struggling with sick pay policies and carryovers of unused sick pay from the year before. That seems like a good one for a paper.