Mine seem to relish worms and baby mice. I have uncovered three mouse nests in the garage over the past two years and rather than leaving the pinkies in the nest to possibly freeze to death (not to mention multiply) I put them in the chicken feeder and quickly walk away. I know it seems cruel, and if we didn't have such a huge mouse problem I would probably be inclined to "bottle feed" those baby mice in order to rescue them. But feeding them to the chickens is quick and carries on the cycle of life. It also means I don't have to set poison baits or traps that might catch a cat's or child's attention.
A lot better than poison baits too... My chickens used to eat baby birds out of the hedge, but that was NOT good >:l
Crickets! They love crickets - when I feel like spoiling them I'll stop and get them a few dozen live crickets at the pet store. I always give the crickets a fighting chance by releasing them in the bushes but those chickens are like predator drones when they see crickets!
They also like carrot tops, which we get for free at the local farmers' market.
They aren't big on scraps, though. Sometimes I'll toss leftover vegetables in their pen and they just turn their little beaks up and ignore it all.
My girls favorite treat of all times is plain old cucumber and of course they love bread - turn their beaks up at white bread but LOVE the heavy grained bread. Sprouted wheat grass and pomegranets, neighbor has a bush/tree.
My chickens LOVE stale whole grain bread, cherry tomatoes, and lettuce. I have to make sure I have enough to go around because they get very vicious when fighting for the treats. They also like going through the tilled up garden and eating dried beans off the trellis, forgotten onions, rotten tomatoes, and mushy peppers.