Finish the sentence.
It's not so much about stereotypes, it's more about what we commonly associate with hobbies and likes and dislikes. For instance, if someone tells me they like going to gallery openings and museums, I might assume they enjoy reading as well.
Unfortunately, though, so many of the assumptions people make when they find out you play video games still hold negative connotations. For instance, for the longest time, those not "in-the-know" really believed that anybody who played video games also read comic books. The comic book thing was also tied in with "Star Wars" and Dungeons & Dragons, too; I guess indulging in any sort of otherworldly fictional fantasy means you're a geek and thus like anything related to fantasy or science fiction.
It also implies immaturity, obviously. But this assumption has never worked with me; I think I read a few Archie comic books at my grandparents' house when I was a kid, but that's it. Never understood the superhero thing, even when it got big in Hollywood. Another popular one involves technology and electronics in general; the belief being that if you play games (especially in this day and age), you're also a big tech or gadget freak. Well, I'm neither. I basically hate all that sh**, believe it or not.
So what are the common assumptions people make about you when they find out you play games? And how often are those assumptions accurate?