Itte kuru, the Te Form of "to go" followed by "to come." Usually upgraded with masu, "Itte kimasu!" is the traditional
expression one uses when going out, and means exactly what it's
supposed to: "I'm going out and coming back." (If you say just ikimasu, the literal
equivalent of "I'm going," it's considered unlucky because it will be interpreted as "going away and not coming back," so avoid saying that unless you really mean it.)