Oxygen and nitrous oxide (N2O) are given alongside inhaled agents, basically, as a medium of transport. These additional agents are the bits that actually do the knocking out and are called vapours.
Isoflurane and sevoflurane are the two vapoursyou need to know about. Generally, isoflurane is used for the maintenance of anaesthesia because it's the similar in terms of effect as sevoflurane but it's less expensive. However, sevoflurane is the drug of choice in gas inductions as it is sweet-smelling and non-irritant (isoflurane is the opposite in both respsects).
Others include:desflurane (very expensive), halothane (old and can cause acute liver failure)
Propofol is the most common. It is a short-acting hypnotic mostly, for the induction of anaesthesia. If you don't know what that drug is, you've never been on an anaesthetic placement. It's the most important drug in anaesthetics. It can be used more maintenance when this done with an IV drug.
Benzodiazepines (especially midazolam) are often used in conjuction with propofol.