Sarcasm 

Snape always seems to talk in a monotone, sarcastic manner. So who knows if he's being sarcastic, serious, or even happy but it makes his character great.

He was sassy 

He seems to have a smart remark for about everything throughout the series, for example calling Hermione an "insufferable know-it-all" or give Ron and Harry the sass all throughout their years.

Unpredictable 

Most of us went throughout the series believing Snape wasn't a "good guy," he sort of just stood between bad and good until we see everything he's actually done for Harry and Dumbledore. We see his story unfold in the final movie and realize how genuine of a person he is and it's honestly just heartbreaking realizing it so late.

Protected Harry 

Harry would have probably died without Snape being around.

Snape protected his as much as he could from Voldermort, saved him at the Quidditch match when Quirrell cursed his broom, and pretty much stayed his secret bodyguard throughout the years, even if Harry didn't know it.

Loyalty 

Snape was insanely loyal.

It took us a while to realize that but he protected Harry because of his unconditional love for Lily. He played a double agent convincing the Dark Lord he was trustworthy and put his own life at risk protecting Hogwarts.