When we discuss "benefits" here at IB, we most commonly refer to insurance products (group health and life, HSA's, etc). Occasionally, we discuss non-traditional benefits (e.g. Sabbaticals and QTEPS), as well.
Recently, though, the Bureau of Labor Statistics polled both private- and public-sector employers to determine which kinds of benefits are most "popular." Perhaps unsurprisingly, vacations and holidays topped the list: