Being able to fluently speak any language.
~ @Kling
Either this or being able to understand complex astrophysical terms. Dimensional and string theory always trip me up, and I hate that there's no resources that don't treat me like I'm either a 4-year-old who's just learning to read or someone with a PhD in astrophysics. I just want to learn, dammit!
If you can't tell, I'm an absolute science nut and I want to be an astrophysicist after I go to university.