Shirts I've gotten comments on that I took as positive:

• "When all else fails, send in the Wookiee."
• A shirt with the Mortal Kombat logo. My father and I have identical shirts; his got someone in a Bst-Buy to chase him down and ask if he could have it. Mine has gotten positive comments from older Chinese women and Tai Chi practicianers.
• "Those who pretend they know everything annoy those of us who do." This one tends to get reactions every time I wear it.
• My Green Lantern shirt has gotten a reaction or two.

But I'm also quite certain that context matters. Family, polite old ladies, nerds (of varying extremes), and Chinese people tend to be the majority of people I interacted with once I got to eighth grade and my anti-idiot filters successfully limited my interactions with anyone else. (Nowadays it's just family, but I've gone into that elsewhere.) I'm sure an "Of course I care! That's why I'm calculating probabilities!" would get (mostly neutral or positive) reactions, but how that translates into real world applications I can only imagine (I physically cannot read body language and a non-negligible number of people might be artificially polite to me because of my eyes).