We always have chocolate coins and a few other sweets,
stickers,
socks,
magic flannel,
something else bath related (bubble bath, bath fizzers etc),
blind bags (will be lego minifigure for the 5 year old, and maybe a star wars vehicle one),
and something cute to poke out of the top (it was a lindt chocolate reindeer last year, this year I have got him a cuddly Scooby Doo).
This year I have also got him one of those plastic slinky springs with an Avengers design, and I plan to get some kind of bag tag for his school book bag, a little kids joke book if i can find a good one, and a die cast Batbike he has his eye on. Last year I got him a mini Lego Superman torch, which he still loves.