Negativity bias (from wikipedia: "Psychological phenomenon by which humans have a greater recall of unpleasant memories compared with positive memories"), or some other modification reducing negativity in my perception of the world for myself.
Maybe toning down scope insensitivity for the whole human race? (I'm not sure if completely eliminating it is a good idea - I don't know if having a brain which feels the correct emotions about arbitrary amounts of suffering would be too traumatic and lead to paralysis. Whatever level of modification that leads to correct actions)
Oh, yes! I'd love to get rid of the negativity bias, I suffer badly from that.
I realize this question is contrived, but I figure it might provoke some fun discussion, so here goes:
If you could push a button and have your brain modified to precisely remove a cognitive bias (and have no other unnecessary effects—most convenient possible world), which would you choose? Why?
What if you were choosing for the whole human race?