Chato is a spanish keyword used in several contexts (at least in Chile), being the two most popular:
as a generic term for a person as in "este chato que vino anoche" (tr. "the guy who came the last night")
as an adjective for being tired or sick of it all. "estoy chato de tanto trabajo" (tr. "I'm sick of all this pile of work").
Also there's a good fella, a friend of mine who uses it as a nickname.