I know what's special about my kids with autism. And I'm talking special interests here -- fascinations, epic collections, subjects of deep knowledge. I'm sure you have some of your own, and people give you gifts in kind, celebrating your passion.
Yet for some reason, we as caregivers are tempted to put a ceiling on these passions when they become uncomfortable for us as spectators. We decide they love Power Rangers a little too much, or they spend a bit too long staring at their Pokémon cards. I get that. We want them to have age-appropriate interests and a broad range of them. The cool thing about many people with autism is they often know what they like (and what they don't) with certainty, and at an early age. Sure, some fleeting affairs of the heart will come and go; but they have a true love. What's so wrong with that?
I recall trying to use my son's Star Wars interest to create a math worksheet when he was in elementary school. I thought using this graphic illustration of a word problem would be motivating for him. The real problem was that he knew much more about Star Wars than I did (still does) and got stuck on my inaccurate labels. (Luke Skywalker wouldn't buy another light saber, for the record; he only has one.) So when you do use your student's interests, make sure your intel is legit.
Or let your student lead the way! Allow him or her to showcase that vast expanse of knowledge, either to a small or larger audience, as a way to celebrate individuality and competence. I know my son's summer school teacher used his special interests to mutual advantage during his reading class. By allowing him to select books in his preferred topic and genre, she was able to get more engagement from him. (See what Paula Kluth has to say on the topic for teachers.)
And at the end of the session, she sent a postcard. The note referred to my middle schooler as a "fantastic leader" and "a pleasure to have in summer class." Imagine that.
So get to know your classmate or student with autism by starting out with their special interests. And be prepared to listen!