I made crackers (well, with a John Lewis kit, so I suppose I assembled them rather than made them) last year, and I am definitely doing it again this year. The kits are on the JL webiste now - thery are sets of six, in two varieties. They come with a snap, joke and hat.
Last year, I put a small bar of Christmas chocolate from Hotel Chocolat into some of them (I think the bars were £2.50 each, and then on some kind of offer, and they were delicious - mince pie flavours, and possibly almond too), Body Shop 60ml bubbles in others (they just fit), small Cath Kidson hand creams in others (you can buy these in a set of three in Waitrose), the smallest Schleich animals in the ones for the children etc.
Kids ones are the easiest, as you can do erasers, sharpeners, lego minifigure etc.
Or you could get the Lego key rings in things lke Indiana Jones for the adults. Or policeman/fireman etc if that corresponds to their job or whatever.
I must get a wriggle on with mine now that I come to think about it. Last year I only had six to do. This year I think I will have 11.