Well, in lieu of the fact that I'm supposed to do stuff relating to relationships involving geeks, I think it would be suitable to talk about gaming, a hobby that many geeks enjoy. As The Game Overthinker points out, there are two types of gamers and two categories of games: Hardcore games, and casual games. Since I'm assuming two hardcore or two casual gamers will not have much of a problem engaging in activities of mutual interest, I will move onto a more clashing problem. This problem that may come up is that you (or your date) may be a hardcore gamer, while the other isn't. They may enjoy playing halo while you might rather enjoy Wii Sports or Bejeweled. Well my friends, don't look so dreary, because I'd like to make a point here that was never really made in Game Overthinker:
It is impossible for someone to not like any type of games.
I'll let that sit in for a moment. Now, some of you probably are ready to jump back with "I never played a game I really liked" or something, but I'd like to expand a bit on what I mean. First off, games. Do you know how many types of games exist out there? Puzzle, action, arcade, rhythm, adventure, platformer, shooters, even board and card games... not to mention subcategories like "bullet hell" or FPS games, or mixed categories like action-adventure or survival horror. But the ultimate point in all this is that there is immense variety here.
Again referencing Game Overthinker, we can start at the beginning with casual versus hardcore games, right? Mmm... no. Because even this line is often blurred by certain games. Let me take the game Rock Band for example. Is playing a guitar like playing Rock Band's guitar? Not really. So certainly the harder difficulty is much more of a "hardcore" gaming experience than a casual one. But, what about the singing? That, on the other hand, I have found to be much more casual, and all it requires is a bit of ability to change one's voice pitch. The best part about Rock Band is that you can have a casual gamer choose singing, and put it on easy, and then you can have your hardcore gamer choose guitar, and put it on hard. Instantly, both players' needs are met, and they can cooperate on completing the song.
This is just a case example, based on my experience. I don't have a wide knowledge of what games are available, but Rock Band I always enjoyed because of this. (Although, yes, I have beaten Half-Life 2, I'm a much more casual gamer in a lot of respects.) But let's say that Rock Band is out of the question, so you and your date need to find something else to satisfy you.
Let's go with a different type of hardcore gamer, one that is much more a... niche: The adventure gamer. Okay, okay, you can stop throwing tomatoes. What I mean by this is that, honestly, adventure gamers like I put up with a ton of BS to solve these games, from ridiculous nonsensical puzzles to logic traps so grand you need sheets of paper to get through them. A lot of casual gamers might get frustrated and angrily give up, not having the hours to devote to clicking here and there.
One thing I know about adventure games though is that there is an odd setup to playing them, in that there are actually two types of people who can enjoy them: Those who enjoy controlling them, and those who like coming along for the ride. It's odd, I know, but I've noticed that when it comes to adventure games some people have to be in control, but others are actually more content to just sit back and watch the game unfold.
So imagine this... it's getting dark, the lights are dim, and you decide to pop Barrow Hill into your computer. (I'll assume you'd be the one playing, just so this story is less grammatically confusing.) So you're controlling the game, as the other leans against you to watch. You walk along the path in the dark woods as suddenly, the lights along the path begin to go out. All you see is the dark sky, and you comfortingly hold closer your date as the lights turn back on to reveal...!
Hey, I'm not spoiling the game.
But this is of course an option if the two of you have the patience to sit through such a game, and work through all the reading and the puzzle-solving and the note-taking. And hey, there are plenty of great adventure games of the freeware variety if you can't spend the money on a commercial game. For paranormal, how about the Ben Jordan series? And horror? The Chzo Mythos (or John DeFoe Quadrology) is a great (although very creepy) choice. Or maybe comedy is more your style, in which case there are some great offerings in even the short game category, like Murder in a Wheel. And fantasy/adventure? How about A Tale of Two Kingdoms?
But let's move on again, and now assume both Rock Band and adventure games are out of the question. What else can you engage in that is gaming? I know Super Smash Brothers has always been pretty playable as long as you go co-op against computer players (casual vs hardcore gamer though... not that fun). The thing to remember here is that the important part is that you enjoy yourselves, and that both of you enjoy playing the game. If nothing else is possible, you could always give in to one side, in which case I'd recommend casual games, seeing as how there's a higher possibility of both liking them. (I know a lot of guys who ace Halo 3 on Legendary yet also love Wii Sports.)
But the most important thing to do is to find the bridge. If you really enjoy gaming, then you can share it. It may take a while, but you will always be able to find a game two people can share and enjoy, regardless of their gaming category. And hey, if console games aren't working out, try checking out the Indie Gaming scene on the PC. Just remember: Perseverance. Games aren't some sort of weird hobby only enjoyed by a few people; they're a form of media, widely ranging in their scope, genre, style, and design. There's so many possibilities that, really, finding a person who cannot like games is impossible.
And hey, if all else fails, try some board games. They're like prehistoric video games.