What groups of employees are the no-brainers to train?

I was doing some benchmarking the other day between a few different organizations. One question that was asked was, what are the "no-brainer" groups of employees to train? (And there may be a second question, what are the no-brainer topics to train, like leadership, ethics, sexual harassment, etc).

To me, the obvious groups are:

• new employees;
• high potential people;
• call center employees;
• sales people; and
• anyone who has to have certification or compliance;
• anyone who has to demonstrate a mastery level (like a pilot, although this differs from organization to organization).

What are other obvious classes of people that should be part of a formal learning program?