Wired has a list of ways to provoke a geek argument. Besides the arguments in the article and the ones provided in the comments at the time of this posting (text editors, Star Wars/Star Trek/Stargate, geeks vs. nerds), the writer forgot a lot. Here are a few of them.
1. We came from monkeys!
(That’s better than using creationism, at least.)
2. Programming language wars. If you’re still using FORTRAN, I have no words.
3. You’re a Capricorn? You two were meant to break up. Your signs aren’t compatible.
4. Comic book heroes. I don’t have to say much more here.
5. Movie adaptations of comic books. Or real books, for that matter.
6. Linux distros. People are very partial to their distro, especially those loyal to less noob-friendly ones.
7. Obviously X is just applied Y. I’m biased because obviously math is purest, but this comic explains it all.
8. Speaking of math, axiom of choice and continuum hypothesis: accept it or not? People really do duke it out over these.