Medically as a pain reliever. The gas used in the medical world is always mixed with oxygen.
As fuel in racing cars.
As a propellant in the food industry for, among other things, whipped cream.
As a drug, laughing gas is presented in balloons and then inhaled. When used like this, nitrous oxide has psychedelic and dissociative effects. The difference between nitrous oxide from these cartridges/cylinder and what is used in hospitals, for example, is that no oxygen has been added. The requirements for medical laughing gas are also higher.