Are most anesthetics strong respiratory irritants, stimulants, regulators or depressants?

Depressants. Most general anesthetic agents (both those given intravenously and those that are inhaled) are strong respiratory depressants because they decrease the body's urge to breathe. Specifically, they eliminate the ventilatory drive in response to hypoxia (low oxygen) and reduce the ventilatory drive in response to hypercarbia (high carbon dioxide). There are, of course, exceptions.