Skeletons, Zombies, and their Nether variants can spawn with equipment, Armor (usually leather, chain, or gold) and have an 8.5 percent chance to drop each piece. They are more likely to spawn with items in Hard mode, or a full Moon.
Iron Golems drop 3-5 iron ingots and 0-2 poppies. His drops aren't affected by Looting enchantment. Naturally spawned Iron Golems can become hostile, if the Player irritates the Villagers.