Any and all of the letters Snape writes to various publications in his head.
All the miscommunications between Snape and Harry; Harry thinks one thing, Snape thinks another...and somehow it all works out.
And, the last Running Gag, Snape's constant, futile denial to how he really feels about things; especially Harry.
The entirety of Snape's shopping for Harry. What's so funny about it? Well, Dumbledore insisted on coming along with him.
The best part? It starts with a description of all the things he's survived and been tortured by...and he treats this as WAY worse!
Had that impertinent, unfathomable, unpredictable child just said that? Had he really referred to Snape as a father, his father? Snape wondered if the flying pigs that must surely have invaded Hogwarts were interfering with Quidditch practice.
The Hogwart's staff's reactions to Snape's new un-greasy hair.
Albus continued to eat calmly, but he was twinkling madly at his plate. Beyond him, Hagrid had missed his mouth entirely and stuck a forkful of bacon into his beard. He too stared at Snape in astonishment, as did Madame Hooch beside him. Quirrell for once appeared to be too surprised even to twitch and stammer, while beyond him Trelawney let out a shriek. "It's a sign! A sign of the apocalypse!"
After Snape scolds Harry for playing with the football inside, he opens the door...and the entire Weasley family falls down.
Snape's opinion of Harry's self preservation instinct.
At this rate, upon learning of Voldemort's plans for him, the boy would march up and challenge the Dark Lord to an arm wrestling match or some other equally idiotic and Gryffindorish duel. He'd probably even take it upon himself to explain to Voldemort what spells and counters he had yet to learn, in the naive assumption the Dark Lord would thereupon avoid using them. Snape could just hear the brat now: "Yoo hoo, Lord Voldemort! I'm over here! Is all the fog from the battle making it hard for you to see me? Aim a little more to your left!"
And any other time Harry gets Voldethingie's name wrong. Including right in front of him.
Master Scary One-eye Sir!
When the Grangers visit the castle, and find every student is so polite. Unaware that Hermione had been using their status as Dentists to build a reputation for herself, and the entire school is terrified that if they eat sweets in front of them, they'll drill holes in their teeth and stuff metal in them!
Snape reminisces finding Lupin in Italy in chapter 27. A nearby waiter thinks they're DATING. Bloody Italians.