This is similar to a "What trait is most important to you" thread.
If you could only use one criteria to meet that special someone (i.e. they are good-looking/pretty, they're funny, they're ambitious, etc... and that's all that you cared about in the person), what would it be?
Also, if you could only use one criteria to choose your best friend, what would it be?
How is this different than a "What trait is most important to you" thread you ask? In this thread, only one trait matters, and you have no control over any other, meaning that if you want a person who is funny, you would be with someone who is smart/dumb, energetic/lazy, etc...
For my special someone, it would have to be confidence, as I find confidence very sexy, and I tend to feed off of it as well.
And as for my best friend, a good listener would be key, as I would like to have someone to tell my problems to and talk about what's going on in my life so that I can work on my problems in life.