(numbered not in order of importance but for reference)

1. Procrastination (for instance, I ought to be finishing a paper instead of writing this list)

2. Overthinking things

3. Not thinking things through enough (not really a contradiction with 2, I don't think), or perhaps best described as "being impulsive"

4. Lack of self-confidence

5. Too much self-critique

6. Getting overly obsessed over things for less than a week (I once convinced myself that I would learn Lojban, and I remained convinced until a couple days later when I decided to just stick to learning Spanish)

7. Being really bad at small talk (I can make small talk about Smalltalk, though! just not traditional small talk...)

8. I can't prevent myself from laughing in the face of terribly serious situations (I just think "oh god, what if I laughed... don't laugh... don't laugh", and then all of a sudden, I'm knee-deep in the funniest situation I've ever been in), particularly if I'm the one that caused the serious situation

9. I have a really bad short-term memory. I actually don't see this as too bad of a flaw, as it's almost a part of my personality/identity.

10. Having a persistent habit of making lists with ten items.

EDIT: formatting fix

I think that 7 and 4 are my biggest flaws, with 1 and 3 closely following those.