This is tough to admit but...Magic: The Gathering. I played as a kid but then grew out of it. Then, recently, a friend of mine told me that someone had made a platform called OCTGN that could be used for a variety of card games including Magic. After some urging, I downloaded it along with a bunch of card packs and he got me back into it, the bastard. These past two months we've been playing 1-2 nights a week online. I haven't told anyone.