I tend to go for wholefoods. More calorific than a Muller Light but not processed so better for you:
(1)banana sprinkled with raw cacoa nibs (chocolate - but it's just the nut, none of the sugar and additives), large tbsp of live Greek yogurt. I get raw chocolate by the kilo from here:
small handful of cashew nuts
small piece of cheese
(personal fave in fact that eat it all the time) some steamed chicken
nectarine/some rasberries/strawberries
Tend to try and snack on unprocessed foods. I do eat yoghurts occasionally for something different but feel that the calories aren't 'worth' it half the time