I'm much much more in the camp of NOT putting a "positive spin" on this question.
I think that became a very in vogue thing to do a decade or so ago...there was some Office episode where Andrew was being interviewed and they said "What are your greatest strengths?" and he said something along the lines of "I work too hard I'm too much of a perfectionist and I spread myself way too thin." The guy looked at him and said "I said strengths... those are weaknesses." (Pause) Andrew (looking both confused and as if he's being very clever): Well...my weaknesses...are...my strengths."
Do a little introspection to come up with a good answer with this question. To quote from "Hitch", they might not want to see it all at once, but they do want to see the real you." So you might not want to say something like "terrible terrible gas", but avoid answers like "I spread myself out too thin because I can't say no." or "I'm too much of a perfectionist" (though I can definitely think of a few people I know where these things ARE a weakness, they're cliche answers).
I think they're just looking to see that you've grown to know yourself over college (a very important aspect of college). They want to see if you know where you're strong, where you're always working to improve as I think these are signs of maturity. If it helps, mine is that I tend to take constructive criticism personally--knowing this, I try to focus on not doing so when I start feeling that way.
I do this too - I always ask for constructive criticism, but if people decide to give it spontaneously I get all defensive until I realize that they're just trying to help me be a better person. I think this is a good thing to talk about because it's honest; it really is a weakness, and when you acknowledge it, you show that you're emotionally aware of yourself and of where you need improvement. At the same time, it's not going to make you seem like damaged goods.
Being brutally open here - other weaknesses:
1. I tend to internalize other people's expectations of me.
2. If a professor or mentor is having a bad day and says something rude to me, I'll feel like it's my fault. Only later will I realize, oh, maybe he's stressed because the grant didn't get renewed. (Sort of the same thing as 1, just internalizing blame instead of expectations.)
3. If someone's having a bad day or is just depressed in general and I don't know what to say (or say something insensitive), I beat myself up about it later, like, a LOT. This would probably be bad to talk about because it sounds like, "My weakness is that I care too much!"
4. Dysutopian novels... and parentheses.
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So, good weaknesses to talk about: 1 and 2. How do I deal with them? I surround myself with positive people, and I try to be more emotionally aware of myself and others.