All chickens like different things- but they usually favor similar foods, such as grass, eggs, seeds, berries, and corn. Here's a basic list of some chicken favorites.
Pretty much all chickens love corn. They can be fed cracked dried corn, but whole kernels of dried corn are usually too large and may pose a hazard. Fresh sweet corn is one of a chicken's favorite foods- they may fed very small amounts of popcorn.
Chickens like to graze, but can be rather picky when it comes to grasses. The grass cannot be too hard, too clingy, or too thin. A favorite of chickens is crabgrass. They don't really care for thinner, hard grasses such as Bermuda. Keep in mind, when feeding grasses, to get them from a pesticide/fungicide/weedkiller-free place to protect the health of your flock.
Worms, grubs, and bugs
These are tempting treats for chickens. Anything that is small and wriggles like a worm (even fingers) can be a chicken's potential meal. Most chickens love to eat grubs and maggots, and some will eat worms, but it's not uncommon for a hen to despise worms. Chickens love to eat bugs, too, but will avoid caterpillars with a grotesque appearance. Mealworms are a favorite. Chickens will also eat small lizards, small snakes, and voles.
Yes, most chickens love to eat eggs. This should be discouraged, to prevent them from eating their own eggs meant for the kitchen.
Seeds are a popular chicken treat. Cantaloupe, small grass seeds, and tomato seeds are readily consumed by most chickens.
Most berries that humans eat are fine for chickens to eat. They love strawberries, blueberries, gooseberries, and currants. Chickens will also eat melons, tomatoes, and apples.