To be as hungry as a horse
(I got this from the) five-finger discount.
A Roland for an Oliver.
A bird in the hand is worth two in the bush.
A danger foreseen is a danger avoided.
A dog does not eat a dog.
A golden key can open any door.
A lie will go round the world while truth is pulling its boots on.
A miss is as good as a mile.
A rolling stone gathers no moss.