16. Have a card up one’s sleeve.
胸有成竹。
17. He cries wine and sells vinegar.
挂羊头,卖狗肉。
18. He takes a spear to kill a fly.
杀鸡用牛刀。
19. In for a penny, in for a pound.
一不做,二不休。
20. It is better to be the head of a dog/lizard than the tail of a lion.
宁为鸡首,不为牛后。