In the final paragraph of The Origin of Species, Charles Darwin leaves us with the vision of Nature as an ‘entangled bank’, where individuals struggle to survive and reproduce in a world of competitors, predators, and parasites. In this chapter, I explore the games animals play in these struggles. Some are behavioural games, resulting in an extraordinary mix of cooperation and conflict in animal families, where sexual partners and parents and their offspring sometimes help one another, but sometimes cheat. Some are games played over evolutionary time, where strategies escalate over the generations between competitors, and between enemies and their victims, leading to extremes, not only in weaponry and cruelty, but in ornamentation and beauty, too. I illustrate these themes especially with examples of mating games in birds and evolutionary arms races between cuckoos and their hosts, to show how the rules of the games can be unravelled by a combination of bird watching and field experiments.