On my reread of the Harry Potter series, I noticed something: Snape is the only person to use the Cloak of Invisibility without Harry's knowledge or consent.
Harry makes a big deal out of it, too:
Harry's fists clenched as they watched Snape skid to a halt next to the tree, looking around [...] "Get your filthy hands off it," Harry snarled under his breath.
-PoA ch. 21
I think there might be something going on here. I know that the Hallows are usually assigned so Snape has the Stone, Harry the Cloak, Voldemort the Wand. But it seems strange that Snape should get the Stone when he has never even touched it, when Harry is the one who canonically says the Stone is the obvious Hallow to choose. Harry longs to join his parents in death (DH ch. 16) and he lets the Stone's shades lead him to his heroic expected end. Dumbledore becomes fatally cursed by his own attempted usage of the Stone to conjure "the figure of a girl" as in the story — in his case, his sister. Snape is constantly presented as being nearly like the sort of person who has the Stone; he did love Lily, she is dead, at one point he did wish he could die too. I've talked about how this makes him like the Bloody Baron. But the thing is, he doesn't allow that "hopeless longing" to drive him mad. He doesn't die by his own hand so that he can see Lily again. To me, at least, he seems less like a Stone sort of person than Harry or Dumbledore. Snape's association with the Cloak is the only other viable Hallow, since Snape never used the Elder Wand and Snape tends to avoid violence.
I think the Cloak suits him well, really; Snape spends the whole story as a spy, an invisible occupation, and he wears the Cloak when symbolically avoiding detection in the area of his death, the Shrieking Shack. I don't think Snape would have been unaware that obeying Voldemort's summons in the battle would mean death. He goes and faces the Shrieking Shack willingly, keeping the secret of the Elder Wand's true master so that someone else can defeat Voldemort and thereby allow others to escape death. In a way, he's bestowing his protection on all the children who were committed to him, much like the third brother and his son. And he greets Death looking into the eyes that first belonged to his old friend Lily. Harry didn't depart with Dumbledore when he was in his King's Cross experience, but Snape is considered to have actually gone on and died. Of all the candidates to go with Dumbledore gladly and treat him as an equal, then, I'd pick Snape.
Of course, from a certain perspective, Harry has all the Hallows since he has united them to master Death. This, I think, explains the good reasons for Harry's association with the Cloak as well as the Stone. But if we must separate them, I argue for Snape with the Cloak every time.
