For starters, let's remember that Severus saved Harry from falling off his broom at our hero's first Quidditch game.He didn't quite succeed, of course, because Hermione was distracting Quirrell.But Snape certainly tried.But we wouldn't have an article if that were his only feat, so let's move on.
Then Severus rushed to the aid of the main trio in the squealing hut. He wanted to save the children from Sirius and Remus, who he thought were threatening wizards.
The fourth year was not without help either.This I think many people did not notice.Snape was strongly against Harry's participation in the tournament of three wizards, because it carried great dangers to the boy.But no one listened to his opinion.
In the Order of the Phoenix, Severus gave Umbridge a pacifier instead of truth serum, which was intended to find out Harry's plans, which of course is not such a feat, but Snape really helped.
He saved Harry after his duel with Malfoy by patching up Draco, who knows how it would have ended without him. Then after Dumbledore's death Snape prevented werewolves from killing Harry.
Severus took the sword of Gryffindor to the lake for Harry.He lured Harry with his patronus - a doe.Before his death he gives Harry his memories to let Potter know the whole truth.And in these memories we see that Lily Potter's son meant a lot to Severus. He does not want the boy to die.