I refer to my best friend as my wife. We've been married for 15 years, but knew each other much longer than that. Basically, she's the other half of me is the best way to describe it. She compliments my logical side by being emotional (in a positive way). She keeps me interested in things I don't usually do while I interest her in things she wished she'd never heard of.

Then of course we have a lot in common as well and even if we weren't married would probably hang out together and go to games and car shows and operas and such.