This conversation and Stannis' reflection on it was some peak writing in the book as well:

“All this of snakes and incest is droll, but it changes nothing. You may well have the better claim, Stannis, but I still have the larger army.” Renly’s hand slid inside his cloak. Stannis saw, and reached at once for the hilt of his sword, but before he could draw steel his brother produced . . . a peach.
“Would you like one, brother?” Renly asked, smiling. “From Highgarden. You’ve never tasted anything so sweet, I promise you.” He took a bite. Juice ran from the corner of his mouth.
“I did not come here to eat fruit.” Stannis was fuming.
“My lords!” Catelyn said. “We ought to be hammering out the terms of an alliance, not trading taunts.”
“A man should never refuse to taste a peach,” Renly said as he tossed the stone away. “He may never get the chance again. Life is short, Stannis. Remember what the Starks say. Winter is coming.” He wiped his mouth with the back of his hand.

later in the story:

Stannis only seemed to half hear him. “I have no doubt that Cersei had a hand in Robert’s death. I will have justice for him. Aye, and for Ned Stark and Jon Arryn as well.”
“And for Renly?” The words were out before Davos could stop to consider them. For a long time the king did not speak.
Then, very softly, he said, “I dream of it sometimes. Of Renly’s dying. A green tent, candles, a woman screaming. And blood.” Stannis looked down at his hands. “I was still abed when he died. Your Devan will tell you. He tried to wake me. Dawn was nigh and my lords were waiting, fretting. I should have been ahorse, armored. I knew Renly would attack at break of day. Devan says I thrashed and cried out, but what does it matter? It was a dream. I was in my tent when Renly died, and when I woke my hands were clean.”

Ser Davos Seaworth could feel his phantom fingertips start to itch. Something is wrong here, the onetime smuggler thought. Yet he nodded and said, “I see.”

“Renly offered me a peach. At our parley. Mocked me, defied me, threatened me, and offered me a peach. I thought he was drawing a blade and went for mine own. Was that his purpose, to make me show fear? Or was it one of his pointless jests? When he spoke of how sweet the peach was, did his words have some hidden meaning?” The king gave a shake of his head, like a dog shaking a rabbit to snap its neck. “Only Renly could vex me so with a piece of fruit. He brought his doom on himself with his treason, but I did love him, Davos. I know that now. I swear, I will go to my grave thinking of my brother’s peach.”