For salty, I go for Laughing Cow Light Original Swiss Flavor cheese + 12 Wheat thins.
For sweet, I go either for Edy's Lime Fruit Bars or a homemade roasted banana and dark chocolate mousse (made with fat free yogurt cheese, roasted bananas, egg whites, cocoa powder, dark chocolate, and sugar). If you can eat nutrasweet/aspartame (I can't) you could go with Sugar Free Jello pudding cups.
For fat (I sometimes just want something fatty), I go with a Light English Muffin (usually multi-grain) and Land O Lakes Light Butter with Canola Oil. The butter flavor usually does it for me.