I get intellectual crushes on people: not for their attractiveness, but for their intelligence. And the feeling attached is more admiration than anything else. Hence my affinity for especially competent professors or polyglots, real or fictional.

• Languages spoken and understood (more languages, and more complex languages, mean more interest)
• Musical talent (I admire people who can play more than one musical instrument or one instrument very well)
• Sense of humor (wit and puns are also appreciated)
• Word play (any sort of twisting of language or the bringing to attention of features of language which most people wouldn't notice or enjoy)