The only true way to end a conversation. Periods end sentences, but "ka-cha"s end discussions. Continuing a conversation after a "ka-cha" has been said is punishable by death in most states, as well as Cuba.
Girl 1: Grrrrl, you should see her prom dress - what a disaster!
Girl 2: Oh, girl, please. It can't be that bad.
Girl 1: It's the ugliest thing this side of Rosie O'Donnell! Ka-Cha!
Girl 2: *silence*